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Cobalt: Its Role in Health and Disease
Abstract
The primarily function of cobalt in humans is based on its role in cobalamin (Cbl, vitamin B12). Therefore, this chapter will focus on the physiological roles of Cbl and the importance of cobalt in human health. Cbl acts as the cofactor for two enzymes, i.e., methylmalonyl-CoA mutase and methionine synthase, in humans. Both enzymes are important for health. In addition, unlike other water-soluble vitamins, there is a unique absorption, delivery, and activation system for Cbl in mammals. Therefore, this chapter will also review the literature on the Cbl transporting system, which is crucial for Cbl function.
... Although Co is an essential trace element for humans [1], excessive intake of Co has been associated with various adverse effects for human health [2]. From an economic point, Co is a critical metal [3] in huge demand for making rechargeable batteries for electric vehicles helping to combat climate change [4]. ...
... Studies confirm that most trace elements have the ability to cross the placental barrier [31]. The maternal and foetal need of Co is well documented [1,30]. In our study, levels of Co in placental tissue were around 0.02 µg/g wet weight, without significant difference between fetal and maternal sides, but the latter is not surprising in view of the anatomical complexity of the placental vasculature [16]. ...
... Neonates are not adults; they may be more susceptible to toxic agents than adults [35]. Co is an essential metal because of its role in the cobalamin synthesis [1]. However, excessive Co intake has been shown to affect the heart, blood, thyroid gland, skin, and immune system and possibly also the DNA [2]. ...
Background
Transfer of the trace metal cobalt (Co) from mother to foetus has not been documented in populations with high environmental exposure to Co, as is the case in the African Copperbelt mining region. We analysed data obtained from 246 mother-infant pairs included (at delivery) in a previously published case-control study on birth defects, done in Lubumbashi (Democratic Republic of Congo) between March 1, 2013, and Feb 28, 2015. Methods: Co was measured by Inductively Coupled Plasma Mass Spectrometry in maternal blood, maternal urine, umbilical cord blood and placental tissue, as available.
Results
The Co concentrations [geometric mean (GM) with interquartile range (IQR)] in maternal blood (GM 1.77 µg/L, IQR 1.07–2.93) and urine (GM 7.42 µg/g creatinine, IQR 4.41–11.0) were highly correlated (Spearman r = 0.71, n = 166; p < 0.001) and considerably higher than reference values determined for general populations elsewhere in the world. The concentrations of Co in umbilical cord blood (GM 2.41 µg/L) were higher (Wilcoxon test, p < 0.001) than in maternal blood (GM 1.37 µg/L), with a correlation between both values (Spearman r = 0.34; n = 127, p < 0.001). Co concentrations in placental tissue (geometric mean 0.02 µg/g wet weight) correlated with concentrations in maternal blood (Spearman r = 0.50, n = 86, p < 0.001) and in neonatal blood (Spearman r = 0.23, n = 83, p = 0.039).
Conclusion
This first study of maternal and neonatal Co concentrations in the African Copperbelt provides strong evidence of a high transfer of Co from mother to foetus.
... In several applications, Co has a similar function to Mn and Zn, and it replaces these elements in biochemical reactions [18]. Co also plays a major role in the biotin-dependent Krebs cycle, in which the body converts sugars into energy [19]. Co-based 2 of 14 nanoparticles are very promising compounds, offering advantages in biomedical-related fields such as magnetic resonance imaging and drug delivery [20]. ...
... Recent research in this domain has expanded to examine the inclusion of cobalt (Co) in different CaP systems [16][17][18][19][20][21][22] as Co is present in bone, dentine, and enamel (at concentrations below 1 ppm). It is also a constituent of vitamin B12 (also known as cobalamin) and could thus play a role in DNA synthesis and neurological function, given that vitamin B12 deficiency is associated with hematologic and neuropsychiatric disorders [16]. ...
... The gradual transformation of brushite to monetite (CaHPO 4 ) at the temperature near~220 • C leads to the release of the chemically bound water [34], and the transformation extends to calcium pyrophosphate (Ca 2 P 2 O 7 ) when the temperature increases tõ 400 • C [7]. These observations are in line with the findings reported here, as heating brushite (BCo0) to 750 • C resulted in approximately a 21.5 wt% mass loss [19], which is closely comparable with a 21 wt% theoretical mass loss [35]. On the other hand, the BCo2-BCo10 sample with a higher ratio of Co/Ca translates as greater mass loss (23-24%). ...
The influence of ionic substitution in the Ca1−xCoxHPO4·nH2O compound was studied systematically for the first time. Among the fascinating features of these biomaterials is that they can be easily tailored for specific applications, for example, as biocements and bioceramics. Different molar concentrations of Co(NO3)2·6H2O, Ca(NO3)2·4H2O, and NaH2PO4·2H2O compounds were employed in determining the starting solutions utilized in the present study. The experimental findings reveal that, when the Co/Ca molar ratio is below 0.67 (BCo4), Co doping (the partial substitution of Ca by Co) takes place in brushite as a monophase. However, in the Co/Ca 0.67–1.5 molar ratio range (BCo4–BCo6), biphasic Co3(PO4)2·8H2O/CaHPO4·2H2O crystals start to precipitate. Full Ca replacement by Co results in the precipitation of nanostructured monoclinic cobalt phosphate and orthorhombic ammonium cobalt phosphate hydrate. Subsequent X-ray photoelectron spectroscopy (XPS), powdered X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses, along with thermogravimetric analysis (TGA), confirmed that the starting solution ratio of Co/Ca had a significant influence on the material’s microstructure, while tuning this ratio ultimately tailored the desired properties of the material for the intended applications.
... Data from more than 10,000 people, among other factors, showed that 46% and 61% have a lower chance of developing lung cancer than those who are not fumigators with the lowest levels of alpha-carotene and beta-cryptoxanthene in the blood. In vitro studies have confirmed that retinoids would inhibit the growth of certain cancer cells, including colon, breast and ovarian carcinoma [12]. ...
... Phylloquinone (K1) or menaquinone (K2) was able to reverse the anticoagulant function of warfarin. It acts by inhibiting the synthesis of vitamin K to reduce the active vitamin K in the body and tissue and therefore vitamin K deficiency [12]. ...
Vitamin is an organic molecule or chemical compounds that is an important micronutrient which is required to act properly in limited amounts for the digestion of the organism. Vitamins are either water-soluble or fat-soluble. Many vitamins do not exist in individual molecules, but belong to similar classes known as vitamers. The multiple functions of vitamin A are essential for growth and development, immune system maintenance and good vision. This vitamin is essential for proper vision by incorporating retinal molecules that absorb light and work during dim light and color differentiation. Due to the unusual role of the retinal as a visual chromophore, vision loss, especially in reduced light. Vitamin D belongs to a class of fat-soluble secosteroids that enhance the absorption of calcium, magnesium and phosphate by the lower intestine and other biological effects. Diet vitamin D is biologically inactive or derived from the synthesis of the skin. Vitamin D controls calcium homeostasis and its metabolism. Vitamin E is a fat-soluble antioxidant that inhibits reactive oxygen species from cell membrane protection. Several biological roles have been postulated, including a fat-soluble antioxidant. Vitamin E serves as a radical scavenger and supplies free radicals with hydrogen (H) atoms. Vitamin K refers to fat-soluble vitamins present in fruit and sold for structurally similar dietary products. For the modulation of certain blood-coagulation proteins or the control of calcium binding in bones and other tissues, the human body requires vitamin K.
... Vitamin B12 is a hydroxycobalamin, and due to the hemin moiety into which cobalt is incorporated, this vitamin is not toxic to humans [59]. Cobalamin functions as a cofactor for two enzymes: methionine synthase and methylmalonyl-CoA mutase [60]. Vitamin B12 deficiency can result in neurological and hematological disorders and may also be a risk factor for coronary heart disease [61]. ...
... Through its similarity to iron (II) ions, cobalt can occupy the Fe 2+ site in the heme porphyrin ring, resulting in a deoxygenated form of the protein. This results in hypoxia, whereby tissues are hypoxic, and the erythropoietin gene is activated in response [60]. It is possible that there is a synergistic toxicity of cobalt and zinc [68]. ...
Iron and cobalt are micronutrients that play an important role in the regulation of cellular processes, being part of the centre of catalases, peroxidases, cytochromes and metalloproteins such as hemoglobin and myoglobin (Fe). Cobalt primarily functions as a component of hydroxycobalamin, which is essential for regulating red blood cell production. Maintaining normal levels of cobalt and iron in the human body is important, as a deficiency can lead to anaemia. These elements are also involved in reactions during which oxidative stress occurs and are therefore considered to be a cause of tumor formation. This paper will discuss aspects of the influence of cobalt and iron on mechanisms that may contribute to the growth of gynecological tumors, as well as other obstetric-gynecological disease entities, by altering the conditions of the microenvironment. In addition, the following review also highlights the role of cobalt and iron in the treatment of gynecological tumors.
... The most important disease known to be caused by B12 deficiency is pernicious anemia. [1] Objectives: We aimed to determine the long-term effects of metal-on-metal (MoM) cobalt (Co)-chromium-containing prostheses used in total knee arthroplasty (TKA) on hearing and tinnitus. Methods: A total of 88 patients with the normal otoscopic examination and normal blood B12 levels, consisting of 44 patients who had been using MoM Co-chromium-containing total knee prosthesis for more than 5 years, and 44 non-implanted patients with similar demographic characteristics, were randomly selected and included in the study. ...
... In Vitamin B12 deficiency, clinics such as methylmalonic aciduria, hyperhomocysteinemia, megaloblastic anemia, and Cbl neuropathy may occur. [1,16] Deficiency is rare in people fed with meat, fish, and milk products, and Vitamin B12 deficiency was not detected in our study patients. ...
Objectives:
We aimed to determine the long-term effects of metal-on-metal (MoM) cobalt (Co)-chromium-containing prostheses used in total knee arthroplasty (TKA) on hearing and tinnitus.
Methods:
A total of 88 patients with the normal otoscopic examination and normal blood B12 levels, consisting of 44 patients who had been using MoM Co-chromium-containing total knee prosthesis for more than 5 years, and 44 non-implanted patients with similar demographic characteristics, were randomly selected and included in the study. Patients with previous ear surgery, chronic middle ear disease, or conductive hearing loss were excluded from the study. All participants were evaluated with pure-tone audiometry (PTA), distortion product otoacoustic emission (DPOAE), tinnitus handicap inventory (THI), and tinnitus reaction questionnaire (TRQ).
Results:
The mean age of the 88 patients was 67.22±10.4 years. The mean age of 44 patients who underwent TKA at least 5 years ago was 72.89±7.18 years, 75% of these patients had bilateral prostheses, and the mean prosthesis duration was 11.00±5.08 years (range 5-25). The two groups were compared statistically using PTA, DPOAE, THI, and TRQ scores. When the patient groups with and without prostheses were compared in terms of hearing and tinnitus, we did not find a significant difference between the two groups (p>0.05).
Conclusion:
In our study, we observed that the long-term use of MoM Co-chromium total knee prostheses did not have an ototoxic effect, contrary to what was believed. We also found that prolonged prosthesis duration or undergoing bilateral surgery did not worsen hearing and tinnitus.
... The primary function of cobalt in humans is predicated on its role in cobalamin. Cobalamin acts as a cofactor for two enzymes, namely, methylmalonyl-CoA mutase and methionine synthase within the human body [1]. ...
Cobalt is a crucial trace element for the human body. It serves as an essentialcomponent of vitamin B12 and plays a pivotal role in the synthesis of amino acids andselect proteins within nerve cells, as well as in the synthesis of neurotransmitters vitalfor the proper functioning of the body. Both excess and deficiency of cobalt can havedetrimental effects on the human body. Notwithstanding the paramount significanceof cobalt as a trace element, comprehensive studies are necessary to evaluate its rolein physiological processes. Keywords: cobalt, human health, trace element, vitamin B12, physiological processes
... Cobalt owns its essentiality mainly to vitamin B12, considering Co is functional part of this vitamin (52). It can enter body trough GI, respiratory and dermal route. ...
Essential trace metals (Fe, Zn, Cu, Mn, Mo, Co) are involved in high number of physiological and metabolic activities and therefore have a substantial role in organisms. Thus, their balance is tightly regulated by levels of absorption, transport, and storage in the organism. They can alter human health in both deficiency and overload conditions. On one hand, deficiency health problems are due to reduction of their physiological activities. On the other hand, Fe, Cu and Co are redox active metals and their increase can cause severe tissue damage through oxidative stress. Numerous well-established diseases like iron and copper deficiency anemia, hemochromatosis, Menkes and Wilson disease, acrodermatitis enteropathica are consequence of essential metal alterations. Nowadays, trace metals alterations are also found to be implicated in neurodegenerative disease, cancers, atherosclerosis, and diabetes. Those diseases represent enormous health problems in contemporary society and trace metals might help to further elucidate their pathogenesis and potentially even treatment. In the present study, essential trace metals kinetic and physiology are reviewed, as well as their roles in disease pathophysiology.
... A direct consequence is the consideration of elements such as Co and Li as critical by number of countries and institutions. Another consequence of the exponent use of these materials is the large amounts of wastes that are generated at all stages of the life-cycle of the products, which potentially results in toxic emissions and hazardous chemicals in landfill [13]. In particular, spent LiBs contain harmful components affecting health and water resources, and can also provoke spontaneous fires. ...
... Chromium and Co are known to have an important role in normal functioning of living organisms, taking part in metabolic reactions (Vincent 2000;Yamada 2013;Margalit et al. 2018), and recent research indicated that Ni, also, could have physiological function in humans (Kumar and Trivedi 2016;Zdrojewicz et al. 2016). In addition to their essential function in the body, in higher concentrations and during longer exposure, Cr, Co, and Ni can pose health risk and ...
The rapid trend of industrialization and urbanization can lead to greater exposure of the general population to chromium, cobalt, and nickel. Their total body burden from all routes of recent exposure, as well as interindividual variability in exposure levels, metabolism, and excretion rates, are reflected in the blood metal concentrations. The main goals in this study were as follows: observing the reference levels of chromium, cobalt, and nickel in the blood of the population living in Belgrade, identification of individual and sociodemographic factors that most affect their blood levels, and comprehension of recent exposure to chromium, cobalt, and nickel. Blood was sampled from 984 participants, voluntary blood donors, who agreed to participate in this study. Individual and sociodemographic data were collected using questionnaire adapted for different subpopulations. Blood metal analyses were measured using ICP-MS method (7700×, Agilent, USA). Our study provided reference values of chromium, cobalt, and nickel in blood for adult population (18–65 years) and confirmed that blood cobalt and nickel levels were mostly influenced by age and gender, and age, respectively. Furthermore, weight status affected blood chromium and cobalt levels, while national origin affected blood chromium levels. The present study highlighted the importance of human biomonitoring studies to monitor exposure status and identify subpopulations with increased exposure to chromium, cobalt, and nickel.
... Cobalt (Co) has an essential role in human health due to its structural function in vitamin B12 synthesis. Given that Vitamin B12 acts as the cofactor for important enzymes [32] and that vitamin B12 deficiency has a causal role in optic neuritis [33] and peripheral neuropathy and demyelination [34], it is possible that reduced Co levels in BP patients may lead to negative effects via B12 deficiency. ...
Purpose
The exact etiology of Bell’s palsy (BP) remains unknown, while its potential etiopathology includes neuritis and inflammation-related demyelination as in optic neuritis. It has been reported that disruption of heavy metal homeostasis may be associated with the inflammatory process of optic neuritis; therefore, heavy metals may be involved in the pathogenesis of facial nerve neuritis. In this study, we aimed to investigate serum levels of heavy metals including essential elements [iron (Fe), zinc (Zn), copper (Cu), cobalt (Co), and manganese (Mn)], and nonessential elements [lead (Pb) and cadmium (Cd)] in patients with BP.
Methods
The study included 25 patients with BP and 31 healthy volunteers. For each participant, serum levels of essential and nonessential elements were measured using the atomic absorption spectrophotometer method.
Results
Serum levels of essential elements were significantly lower in the patient group compared to the control group (p < 0.001, for each). Serum levels of Pb increased in the patient group compared to the control group although no significant difference was achieved (p = 0.105). In contrast, serum Cd levels increased significantly in the patient group compared to the control group (p < 0.001).
Conclusion
Our findings suggest that decreased essential and increased nonessential elements may be associated with BP and thus, serum concentrations of these elements should be taken into account in BP. Studies are warranted to determine the role of these elements in treatment of BP.
... Mn is considered an essential component as a cofactor for numerous metalloenzymes involved in metabolism, and it is related to the nervous system [39,40]. Co is essential because it is a component of vitamin B12, which is involved in multiple biological functions [41]. Co-poisoning is associated with weight loss, loss of appetite, weakness, increased hemoglobin, and red blood cell counts [42]. ...
Protein supplements (PS) are trendy foods, especially those made from whey. In addition to providing protein, these products are a source of metals, providing essential elements (Na, K, Mg, Ca, Mo, Mn, Fe, Co, Cu, and Zn) and other potentially toxic elements (Al, B, Sr, V Ba, and Ni). In this study, 47 whey PS samples were analyzed for mineral elements by ICP-OES, and their dietary exposures were assessed for three consumption scenarios. Elements found in higher concentrations were K (4689.10 mg/kg) and Ca (3811.27 mg/kg). The intake of 30 g PS (average recommended amount/day) provides about 20% of the established reference value (NRI) for Cr (18.30% for men and 25.63% for women) and Mo (26.99%). In a high daily consumption scenario (100 g PS/day) and when the maximum concentrations are considered, Cr, Zn, Fe, Mo, and Mg dietary intakes of these metals exceed the daily recommended intakes and could pose a risk. The daily intake of 30, 60, and 100 g of whey PS for 25 years does not pose a health risk since the hazard index (HI) is less than one in these consumption scenarios, and the essential elements contributing most to HI are Co, followed by Mo and Cr. It is recommended to improve the information to the consumers of these new products. Furthermore, to help in the management and prevention of these potential health risks, it would be advisable to improve the regulation of these dietary supplements and their labeling.
... Gastrointestinal absorption is relatively low and depends on the solubility of the Cobalt compound which enters the body. If not used for Vitamin B12 formation, most of the absorbed Cobalt becomes attached to the serum albumin and other blood proteins and is eliminated through kidneys with urine [18]. Nevertheless, in high doses, Cobalt may cause acute toxic reactions or adverse effects in cases of continuous chronic exposition. ...
Background:
CAD/CAM technologies facilitate using powder CoCr alloys to produce metal-ceramic dental restorations. However, base alloys may induce oxidative stress in the oral cavity due to corrosion and ion release. This study evaluated resistance to corrosion and release of metal ions from 3D printed CoCr dental alloy and their effect on oral oxidative stress.
Methods:
Metal-ceramic crowns with 3D printed copings from CoCr alloy EOS CobaltChrome SP2 (EOS, Germany) were fabricated for 35 patients. Inductively coupled plasma mass spectrometry (ICP-MS) was used for measuring the concentration of Co and Cr ions in non-stimulated saliva before prosthetic treatment (BPT), at 2 h and 7 days after the dental treatment (APT2, APT7, respectively). Open circuit potentials (Eocp) were evaluated at APT2 and APT7. Estimating oral oxidative stress, measurements of 8-isoprostaglandin F2-alpha were conducted using liquid chromatography-tandem mass spectrometry (LC-MS/MS) at stages BPT, APT2, and APT7.
Results:
Salivary Co level increased at APT2 and decreased to the initial levels at APT7. No statistical difference was found between the levels of 8-isoPGF2-alpha measured, and between the Eocp measurements at APT2 and APT7.
Conclusions:
The studied alloy showed stable corrosion resistance and the metal ion release did not induce oral oxidative stress.
... Кобальт также является частью биотинзависимого цикла Кребса -процесса, который организм использует для расщепления сахара и превращения его в энергию. [2,3] Кобальт в еде ...
В статье рассмотрены основные свойства кобальта (Co) и его воздействие на организм человека. Проведен систематический обзор современной специализированной литературы и актуальных научных данных. Указаны лучшие натуральные источники кобальта. Рассмотрено использование минерала в различных видах медицины и эффективность его применения при различных заболеваниях. Отдельно проанализированы потенциально неблагоприятные эффекты кобальта на организм человека при определенных медицинских состояниях и заболеваниях. Расширенная HTML версия статьи приведена на сайте edaplus.info.
... In the homogeneous Co 2+ /PMS system, cobalt ions can almost accomplish self-circulation, so it possesses high oxidizing ability, efficient removal of organic pollutants, and high activity. However, Co 2+ is a kind of heavy metal ion whose toxicity cannot be ignored, which is easy to cause secondary pollution and further induces health problems such as asthma and pneumonia (Yamada, 2013). ...
In this study, the walnut shell (WS) supported CoFe2O4 nanopowder material (CoFe2O4/WS) were synthesized and characterized by X-ray diffraction, scanning electron microscopy, fourier transform infrared spectrometer, transmission electron microscope and X-ray photoelectron spectroscopy. The CoFe2O4/WS exhibited excellent catalytic activity in the process of activating peroxymonosulfate (PMS) to degrade ofloxacin (OFL). The results showed that 92.8% of OFL removal efficiency and 76.1% of mineralization rate were achieved at 1 g L–1 CoFe2O4/WS, 1 g L–1 PMS within 30 min. Moreover, the results of coexisting anions and organic matter indicated that the CoFe2O4/WS/PMS system has a certain anti-interference ability in complex environment. Furthermore, radical identification experiment demonstrated that SO4·− was the dominant active substance during the OFL degradation process, and a possible activation mechanism of PMS by CoFe2O4/WS was proposed. Finally, possible degradation pathways of OFL were inferred based on the reaction intermediates detected by high-performance liquid chromatography-mass spectrometry. These findings will enrich the understanding of sulfate radical-advanced oxidation process (SR-AOPs) for antibiotic wastewater treatment and will guide the development of metal-organic frameworks as catalysts for PMS.
... It has been well established that excessive bodily exposure to cobalt can damage human health [35]. Moreover, increasing evidence has demonstrated the neurotoxicity of cobalt in both in vivo and in vitro models [52,54]. In particular, our previous study has revealed that people with a median blood cobalt level of 2.514 μg/L (less than the safety threshold of 10 μg/L) are still able to develop neurodegenerative changes, suggesting taht the mechanism behind cobalt-induced neurodegeneration has yet to be fully unveiled [55]. ...
Cobalt is the most widely used heavy metal pollutant in medicine and industry. Excessive cobalt exposure can adversely affect human health. Neurodegenerative symptoms have been observed in cobalt-exposed populations; however, the underlying mechanisms remain largely unknown. In this study, we demonstrate that the N6-methyladenosine (m6A) demethylase fat mass and obesity-associated gene (FTO) mediates cobalt-induced neurodegeneration by impairing autophagic flux. Cobalt-induced neurodegeneration was exacerbated through FTO genetic knockdown or repression of demethylase activity, but was alleviated by FTO overexpression. Mechanistically, we showed that FTO regulates TSC1/2-mTOR signaling pathway by targeting TSC1 mRNA stability in an m6A-YTHDF2 manner, which resulted in autophagosome accumulation. Furthermore, FTO decreases lysosome-associated membrane protein-2 (LAMP2) to inhibit the integration of autophagosomes and lysosomes, leading to autophagic flux damage. In vivo experiments further identified that central nervous system (CNS)-Fto-specific knockout resulted in serious neurobehavioral and pathological damage as well as TSC1-related autophagy impairment in cobalt-exposed mice. Interestingly, FTO-regulated autophagy impairment has been confirmed in patients with hip replacement. Collectively, our results provide novel insights into m6A-modulated autophagy through FTO-YTHDF2 targeted TSC1 mRNA stability, revealing cobalt is a novel epigenetic hazard that induces neurodegeneration. These findings suggest the potential therapeutic targets for hip replacement in patients with neurodegenerative damage.
... Cobalt (Co) has a variety of (mainly industrial) applications [98]. As a basic component of vitamin B12, it is an essential micronutrient for humans [99]. In humans, cobalt deficiency is most often observed, but there are some cases of cobalt poisoning [100]. ...
The study of bottom sediments was conducted within the basins of water bodies used for recreational purposes (e.g., bathing, fishing and diving) in the Silesian Upland and its periphery in southern Poland. Various concentrations of trace elements were found in bottom sediments, reflected by the following levels: Pb (30-3020 mg/kg), Zn (142-35,300 mg/kg), Cd (0.7-286 mg/kg), Ni (10-115 mg/kg), Cu (11-298 mg/kg), Co (3-40 mg/kg), Cr (22-203 mg/kg), As (8-178 mg/kg), Ba (263-19,300 mg/kg), Sb (0.9-52.5 mg/kg), Br (1-31 mg/kg), Sr (63-510 mg/kg) and S (0.001-4.590%). These trace elements are present in amounts that usually exceed those found in other bodies of water or are sometimes even unprecedented among bodies of water in the world (e.g., cadmium-286 mg/kg, zinc-35,300 mg/kg, lead-3020 mg/kg, arsenic-178 mg/kg). It was found that bottom sediments were contaminated to varying degrees with toxic metals, metalloids and non-metals, as evidenced by the values of geoecological indicators, i.e., the geoaccumulation index (−6.31 < I geo < 10.90), the sediment contamination factor (0.0 ≤ C i f < 286.0), the sediment contamination degree (4.6 < C d < 513.1) and the ratios of the concentrations found to the regional geochemical background (0.5 < I RE < 196.9). It was concluded that the presence of toxic elements (e.g., lead, zinc, cadmium, chromium, strontium and arsenic) in bottom sediments should be taken into account when classifying water bodies as suitable for recreational use. A maximum ratio of the concentrations found to the regional geochemical background of I RE ≤ 5.0 was proposed as the threshold for the permissibility of recreational use of water bodies. The water bodies used for recreational purposes in the Silesian Upland and its periphery do not meet the geoecological conditions for safe use in terms of recreation and leisure activities. Forms of their recreational use that directly affect the participants' health (e.g., fishing and the consumption of fish and other aquatic organisms) should be abandoned.
... A direct consequence is the consideration of elements such as Co and Li as critical by number of countries and institutions. Another consequence of the exponent use of these materials is the large amounts of wastes that are generated at all stages of the life-cycle of the products, which potentially results in toxic emissions and hazardous chemicals in landfill [13]. In particular, spent LiBs contain harmful components affecting health and water resources, and can also provoke spontaneous fires. ...
... Its exposure at controlled levels helps in the metabolism of living beings. Additionally, cobalt is used as part of the treatment of some diseases [8]. However, the excess release of this element has reached maritime bodies, such as rivers, lakes and oceans, and its high exposure causes the development of cardiac anomalies and carcinomas in living beings due to its constant exposure to this material [9]. ...
In this paper, we report the preliminary results regarding the use of fluorescent dye calcein (C30H26N2O13) as a sensor for the detection of cobalt levels in aqueous solutions. The sensor cell based on calcein is built by fixed-in layers by means of thermoplastic polyurethane (TPU) and adjusted to pH = 7. The layer shows a fluorescence emission in the range of λ = 545 nm to 570 nm when it is excited by optical fields at a wavelength centered at 465 nm. By the contact of different cobalt concentrations with the calcein layer structure, quenching of the fluorescence intensity is observed. The results indicate that the sensor exhibits a linear response of the fluorescence quenching related to the cobalt concentration level in the range of 10−5 to 10−3 mol/L. Additionally, the proposed sensor has a simple experimental set-up, low cost, and does not require additional complex instrumentation.
... The data are taken from the USDA National Nutrient Database for Standard Reference (https://ndb.nal.usda.gov/ndb/) displays the most important micronutrient for vegans to be aware of (Guetterman et al. 2022;Mikkelsen and Apostolopoulos 2019;Stabler 2013;Yamada 2013). In addition, recent reports suggest that B12 might improve immunity against infections (dos Santos 2020; Shakoor et al. 2021). ...
... Copper (Cu) is also an essential enzyme components for active cellular metabolism and physiological processes such as good bone formations and production of haemoglobin, antioxidants, neurons protections and other oxidative stress-associated enzymes [46]. Similarly, Co is an important micronutrient needed for production of vitamins and other co-factors for enzymes [47]. On the other hand, living cells require the less toxic biological usable form (Cr 3+ ) for the production of tolerance factors of glucose for carbohydrate, proteins and fat metabolisms [46]. ...
Maize is a vital nutritional cereal for the infants, young children and adults. The environment which they are cultivated in Africa could expose to metal accumulations from soils, thereby posing health risks to the consumers. The objectives of this study were determine metal accumulations in maize grains (Zea mays L.) cultivated close to Gosa and Gwagwalada solid waste dumpsites and their health risks via consumption. A total of 36 soil samples (12 each from dumpsite soil, farmland soil and maize grains) were collected and analyzed for some metals [cadmium (Cd), lead (Pb), zinc (Zn), cobalt (Co), copper (Cu), chromium (Cr), nickel (Ni) and mercury (Hg)] using standard atomic adsorption spectrophotometer. The transfer factors and metal health risks in adults (60 kg; 22-48.9 years), young children (35 kg; 6-15 years) and infants (15 kg; 1-6 years) were evaluated using mathematical models. The ranges of metal (mg/kg) detected were 10114.00 to 0.52, 10.45 to 0.001 and 13.62 to 0.001 for dumpsite, farmland and maize grains, respectively. Though, within FAO/WHO and EU safe limits, Zn was significantly (p<0.05) highest in both locations, while Cd, Cr and Hg (0.001 mg/kg) were the least. Only Zn had transfer factor value below 0.5, which indicates possibilities of anthropogenic elevations. The estimated daily intake from consumption of maize grains (57 g) were generally high for Zn and low for Ni, Cd, and Hg in exposed individuals. The hazard index was below 1, which indicates no significant non-carcinogenic risks in exposed populations. The incremental lifetime cancer risks was below 10-6 and this suggest potential lifetime cancer risks in the order infants ? children ? adults. This study concluded that daily consumption of maize cultivated closed to dumpsites poses potential lifetime cancer concern and thus maize farming around dumpsites needs to be discouraged for safety reasons.
... The most chemically complicated vitamin is vitamin B12, which is also the only vitamin that must be obtained from meals or supplements produced from animals for humans. 2 Only a few types of bacteria can produce vitamin B12. The majority of individuals in industrialized countries obtain adequate B12 from eating meat or other foods derived from animals. ...
Vitamin B12 is essential for the development of healthy nerves and red blood cells. Vitamin B12 deficiency is becoming widespread and most commonly affects the elderly, pregnant women, vegetarians, and patients with renal or intestinal diseases. Either parenteral vitamin B12 treatment or high-dose oral vitamin B12 treatment is an effective therapy regardless of etiology. Parenteral therapy using the intramuscular route is considered the most familiar treatment for vitamin B12 deficiency. Anaphylactic reaction after intramuscular injection is an uncommon and potentially serious side effect. In this study, we are documenting a case of anaphylactic reaction in a 50-year-old man after her second dose of intramuscular injection of cyanocobalamin. The purpose of this case report is to highlight the need to understand the rare life-threatening side effect of intramuscular cyanocobalamin. Health care providers should be vigilant while administering the intramuscular injection of cyanocobalamin to vitamin B12 deficient patients.
... Zn is the essential component of Zn-binding proteins in the human body, and has been recognized as essential for prenatal and postnatal growth [50]. Co is an essential trace element for humans, as it is a key constituent of vitamin B12 [51], but the role of Co in fetal development needs further investigation. ...
The understanding of the impact of prenatal exposure to metal mixtures on birth weight is limited. We aimed to identify metal mixture components associated with birth weight and to determine additional pairwise interactions between metals showing such associations. Concentrations of 18 metals were measured using inductively coupled plasma mass spectrometry in urine samples collected in the 3rd trimester from a prenatal cohort (discovery; n = 1,849) and the Healthy Baby Cohort (replication; n = 7,255) in Wuhan, China. In the discovery set, we used two penalized regression models, i.e., elastic net regression for main effects and a lasso for hierarchical interactions, to identify important mixture components associated with birth weight, which were then replicated. We observed that 8 of the 18 measured metals were retained by elastic net regression, with five metals (vanadium, manganese, iron, cesium, and barium) showing negative associations with Z-scores for birth weight and three metals (cobalt, zinc, and strontium) showing positive associations. In replication set, associations remained significant for vanadium (β = -0.035; 95% confidence interval [CI], -0.059 to -0.010), cobalt (β = 0.073; 95% CI, 0.049 to 0.097), and zinc (β = 0.040; 95% CI, 0.016 to 0.065) after Bonferroni correction. We additionally identified and replicated a single pairwise interaction between iron and copper exposure on birth weight (P < 0.001). Using a two-stage analysis, we identified and replicated individual metals and additional pairwise interactions-associated birth weight. The approach could be used in other studies estimating the effect of complex mixtures on human health.
... Vitamin B12 (cobalamin [Cbl]) is an essential water-soluble vitamin that involved in onecarbon metabolism (4). Vitamin B12 is a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism (5). It is particularly important in the normal functioning of the nervous system via its role in the synthesis of myelin (6), and in the maturation of developing red blood cells in the bone marrow. ...
Background and objectives: Breast carcinoma is one of the most common
malignant diseases among women worldwide. In Iraq there are noticeable
elevation in incidence rates and prevalence of advanced stages of breast cancer.
Cobalamin (vitamin B12) is essential micronutrient involved in one carbon
metabolism and DNA methylation, which affects cancer. All of these may be
change in breast cancer. The present work was designed to estimate and compare
serum vitamin B12 among female breast cancer patients (60 ones) and healthy
control subjects (60 ones) in Sulaimania city.
Methods: This is a case-control study conducted on sixty cases of newly
diagnosed women with breast cancer, the control group include sixty healthy
women. Serum vitamin B12 levels were estimated by electrochemiluminescence
immunoassay (Elecsys) method. Data was analyzed using the software SPSS
(Ver. 22) including frequency and percentage for categorical variables. Pearson
chi-square test was used for analysis of all categorical variables.
Results: In this study we found that serum vitamin B12 levels were significantly
(p=0.01) lower in breast cancer patients as compared to healthy control subject.
There was no association between serum vitamin B12 levels with estrogen,
progesterone, and HER2 receptor.
Conclusion: Given the results, it can be concluded that serum vitamin B12 is
consistently lower among breast cancer patients. There was no association
between serum vitamin B12 levels and hormones receptors status, indicating
clinical implications for the interpretation of serum vitamin B12 levels.
Therefore, it should be taken into consideration by physicians and cancer
specialists.
... Vitamin B12 (cobalamin [Cbl]) is an essential water-soluble vitamin that involved in onecarbon metabolism (4). Vitamin B12 is a cofactor in DNA synthesis, and in both fatty acid and amino acid metabolism (5). It is particularly important in the normal functioning of the nervous system via its role in the synthesis of myelin (6), and in the maturation of developing red blood cells in the bone marrow. ...
the research was about evaluating serum vitamin B12 in 2 groups first one in newly diagnosed breast cancer women (before taking any chemotherapy or radiation treatment ) and healthy control women
... Cobalt-containing complexes are one such class of metal complexes, that can be effective as alternative metal-based chemotherapeutics instead of platinum compounds [3,[11][12][13]. The necessary trace element cobalt plays many important physiological roles in human biological systems, including DNA synthesis, formation of red blood cells, and maintaining the health of nerves [14]. This indicates that the human body system can tolerate the excess cobalt overburden. ...
Aims
Metal complexes have ignited considerable interest in the field of chemotherapy after the serendipitous discovery of cisplatin but the severe toxicity of these platinum-based drugs compelled researchers to search for newer, more effective lesser toxic anticancer drugs.
Materials and methods
Structural analysis is done by different physicochemical techniques including X-ray single crystallography. Toxicity study has been done in normal Swiss albino mice. MTT assay assessed cell viability. Apoptosis, cell cycle arrest, and cell proliferation were assessed by FACS using Annexin V-PI, PI, and CFSE staining respectively. Western blot quantifies protein expression. While cell migration was studied by wound healing assay.
Key findings
One-pot synthesis of a novel mononuclear cobalt(III)-Schiff base complex (1) (>99 % purity) and its complete characterization have been done. Cell viability assay showed that 1 (IC50 = 16.81 ± 1.33 μM) exhibits cytotoxicity at much lower concentration in comparison to oxaliplatin (IC50 = 31.4 ± 0.69 μM) against MCF-7 cells for 24 h of therapy without being overly toxic to human PBMCs (IC50 ≥ 60 μM). Additional in vitro studies demonstrated that 1 induces apoptosis via G2-M cell cycle arrest and reduces cell proliferation as well as cell migration in MCF-7 cells. In vivo subacute toxicity (28 days) and systemic chronic toxicity (40 days) studies were carried out in normal Swiss albino mice showed 1 is significantly nontoxic to the host.
Significance
The readily synthesizable, significantly nontoxic cobalt complex with appreciable anticancer activity implies that it might be an effective chemotherapeutic agent for new-age anti-tumor medication.
... The compounds of cobalt are used as a drying agent in paints lacquers and coloring agents for potter ceramics and glass industries [84]. It also plays a very important in different physiological processes, is essential to the metabolism in all animals [85]. However, its excessive intake leads to different toxicological effects such as cardiomyopathy, asthma, allergic dermatitis, and other toxic effects [86][87][88]. ...
Thiourea and its derivatives display several electronic and structural features which enable its application in various fields, ranging from biological to non-biological. These compounds contain heteroatom's like sulfur and nitrogen, which are nucleophilic and allow for establishing inter-and intramolecular hydrogen bonding. In addition, they also provide coordination sites to act as ligands in the field of coordination chemistry. Due to these properties, thiourea derivatives are used as chemosensors to detect various metal cations. This article covers a broad range of thiourea based chemosensors that are used for colorimetric and fluorimetric (turn-off and turn-on) detection of different cations such as Ag⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Mn²⁺, Cu²⁺, Co²⁺, Al³⁺, Cr³⁺, Ga³⁺, In³⁺, Ru³⁺, and Fe³⁺, etc., in various biological, agricultural and environmental samples. Structural parameters and coordination mechanism of each sensor with metal ions have been discussed. Further, the sensing performances of thioureas derivatives have been compared and discussed, which could help the readers for the future design of highly sensitive and selective organic fluorescent and colorimetric chemosensors to detect metal cations.
... As in humans, cobalt as part of vitamin B12 is an essential micronutrient in experimental animals. However, cobalt deficiency has been described in ruminants (e.g., sheep, goats, and cattle) raised in areas with very low cobalt (Yamada 2013). Cobalt supplements were beneficial in these cases because cobalamin can be synthesized by gut bacteria and absorbed. ...
Introduction: Cobalt is a transition element and a component of more than 70 naturally occurring minerals. It is often combined with other metals to make metal alloys or cemented carbides for a variety of medical or commercial applications; some cobalt compounds are used as pigments or in electronic devices. People can be exposed to cobalt or its compounds in workplaces that use or produce cobalt, from cobalt-containing orthopedic joint replacements that release cobalt ions from wear and tear, and from the environment. Exposure to cobalt from food and water is generally limited.
Methods: The National Toxicology Program (NTP) evaluated evidence for human exposure, cancer studies in humans and experimental animals, mechanisms of carcinogenesis, and other relevant information, including evaluating study quality, integrating the evidence across studies, and integrating evidence across data streams (mechanistic, animal, and human data). Using established criteria, NTP reached conclusions on the strength of evidence for the carcinogenicity of cobalt from cancer studies in experimental animals and humans, and the final listing recommendation was reached by applying the Report on Carcinogens (RoC) listing criteria to the body of evidence.
Results and Discussion: The physicochemical properties, toxicokinetics, mechanistic data, and other relevant data for cobalt and cobalt compounds were used to identify and compare the chemical and biological properties and events that are relevant to cobalt-induced carcinogenicity to determine if a group listing for cobalt and cobalt compounds that release cobalt ions in vivo was warranted.
Cancer studies in experimental animals: NTP concluded that there was sufficient evidence of carcinogenicity in animals based on its review of 16 rodent carcinogenicity studies. Exposure of experimental animals to cobalt metal or cobalt compounds (both water-soluble and poorly water-soluble compounds) caused tumors in rats and/or mice through several different routes of exposure and at several different tissue sites. Inhalation exposure to cobalt metal or cobalt sulfate caused lung tumors in rats and mice as well as tumors of the pancreas (male rats only), the adrenal gland (male and female rats for cobalt metal and female rats for cobalt sulfate), and the hematopoietic system (female rats exposed to cobalt metal only). Intratracheal instillation of cobalt oxide also caused lung tumors in rats. In addition, local injection of rats with cobalt or cobalt compounds at various anatomic locations caused tumors at the injection sites, including intraperitoneal or intramuscular injection of poorly water-soluble cobalt oxide, subcutaneous injection of water-soluble cobalt chloride, and intramuscular or intrathoracic injection of cobalt metal or nanoparticles.
Mechanistic data: The key events related to toxicity and carcinogenicity of cobalt and cobalt compounds are thought to include cellular uptake of cobalt, intracellular release of cobalt ions from particles, and immediate and downstream biological responses related to the proposed modes of action. These events are applicable to all cobalt forms that release cobalt ions in vivo, including water-soluble and poorly water-soluble particles. The biological responses include inhibition of DNA repair, genotoxicity, generation of reactive oxygen species resulting in oxidative damage, and stabilization of hypoxia-inducible factor 1α, a protein that increases the expression of genes that promote survival of cells that receive less oxygen.
Human cancer studies: NTP concluded that the data available from studies in humans were inadequate to evaluate the relationship between human cancer and exposure to cobalt and cobalt compounds that release cobalt ions in vivo. Although increased risks of lung cancer were found in most of the five cohort studies, it is unclear that the excess risks were due to exposure specifically to cobalt, because of potential confounding from exposure to known carcinogens or other study limitations.
NTP Hazard Conclusion and Significance: The conclusion of the cancer hazard evaluation was that cobalt and cobalt compounds that release cobalt ions in vivo should be listed as reasonably anticipated to be human carcinogens in the RoC. The Secretary of Health and Human Services approved the listing of cobalt compounds that release cobalt ions in vivo in the 14th RoC. The rationale for the listing was sufficient evidence of carcinogenicity from experimental animals and evidence from studies on mechanisms of carcinogenesis that indicate that the release of cobalt ions is a key event for cobalt-induced carcinogenicity.
... Vanadium is an enzyme cofactor in hormone, glucose, lipid, bone and tooth metabolism 34 . Cobalt is an important component of vitamin B12 35 . The average content of 53 Cr, 61 Ni, 51 V, 77 Se and 59 Co was 1.2, 1.0, 0.7, 0.2 and 0.1 ug/g, respectively. ...
Multi-elemental analysis is widely used to identify the geographical origins of plants. The purpose of this study was to explore the feasibility of combining chemometrics with multi-element analysis for classification of Codonopsis Radix from different producing regions of Gansu province (China). A total of 117 Codonopsis Radix samples from 7 counties of Gansu province were collected. Inductively coupled plasma mass spectrometry (ICP-MS) was used for the determination of 28 elements (³⁹ K, ²⁴ Mg, ⁴⁴Ca, ²⁷Al, ¹³⁷Ba, ⁵⁷Fe, ²³Na, ⁸⁸Sr, ⁵⁵Mn, ⁶⁶Zn, ⁶⁵Cu, ⁸⁵Rb, ⁶¹Ni, ⁵³Cr, ⁵¹ V, ⁷Li, ²⁰⁸Pb, ⁵⁹Co, ⁷⁵As, ¹³³Cs, ⁷¹ Ga, ⁷⁷Se, ²⁰⁵Tl, ¹¹⁴Cd, ²³⁸U, ¹⁰⁷Ag, ⁴Be and ²⁰²Hg). Among macro elements, ³⁹ K showed the highest level, whereas ²³Na was found to have the lowest content value. Micro elements showed the concentrations order of: ⁸⁸Sr > ⁵⁵Mn > ⁶⁶Zn > ⁸⁵Rb > ⁶⁵Cu. Among trace elements, ⁵³Cr and ⁶¹Ni showed higher content and ⁴Be was not detected in all samples. Intra-regions differentiation was performed by principal component analysis (PCA), cluster analysis (CA) and supervised learning algorithms such as linear discriminant analysis (LDA), k-nearest neighbors (k-NN), support vector machines (SVM), and random forests (RF). Among them, the RF model performed the best with an accuracy rate of 78.79%. Multi-elemental analysis combined with RF was a reliable method to identify the origins of Codonopsis Radix in Gansu province.
... Vitamin B12, commonly known as cobalamin, is a cofactor in DNA synthesis, fatty acid, and amino acid metabolism [115]. Vitamin B12 is a cobalt coordination complex that occupies the center of a corrin ligand and is further linked to an adenosyl group and benzimidazole ligand [116]. ...
The effects of a sufficient amounts of vitamins and nutrients on the proper function of the nervous system have always been regarded by scientists. In recent years, there are many studies have been done on controling or improving the symptoms of neurological and behavioral disorders which is created by changes in the level of vitamins and other nutrition, such as omega-3 and iron supplements. Autism spectrum disorder (ASD) is a neurodevelopmental disorder that causes disruption individual communication, especially in social interactions. Its symptoms include anxiety, violence, depression, self-injury, trouble with social contact and pervasive, stereotyped, and repetitive behavior. ASD is most noticeable in early childhood. Attention Deficit Hyperactivity Disorder (ADHD) is a lasting pattern of inattention with or without hyperactivity that makes functional disrupt in daily life. ADHD symptoms included; impulsivity, hyperactivity, inattention, restlessness, talkativeness, excessive fidgeting in situations as sitting, meetings, lectures, or at the movies, boredom, inability to make decisions, and procrastination. The exact etiology of ADHD has not yet been found, but several observations have been assumed the reduced function of the brain lead to deficits in motor planning and cognitive processing. It has been shown that Pro-inflammatory cytokines and oxidative stress biomarkers could be increased in both ASD and ADHD. Several studies have been done to illustrate if vitamins and other dietary supplements are effective in treatment and prevention of ASD and ADHD. In this review, we aim to evaluate the effects of vitamins and other dietary supplements (e.g., melatonin, zinc supplements, magnesium supplements) on ASD and ADHD.
... Cobalt being an essential trace element, performs several crucial tasks in human biological systems and is abundantly present in cobalamin. The different forms of cobalamin are essential for different biological activities like the synthesis of DNA and its regulation, red blood cells formation, and the preservation of healthy brain and nerve activity [15]. In humans, cobalamin possesses distinct roles in catabolism of mitochondrial fatty acids and metabolism of cytoplasmic amino acids [16,17]. ...
Research on metal-based chemotherapeutics gained tremendous impetus after the groundbreaking discovery of cisplatin and related complexes as potential anticancer agents. Unfortunately, applications of these platinum-based coordination complexes have become restricted owing to their toxicity and drug-resistant properties. Keeping these facts in mind, several groups studied cobalt complexes coordinated with Schiff base ligands. Cobalt has been found to be less hazardous to humans than platinum, and a cobalt(III) Schiff base complex, Doxovir, has advanced to the phase-II antiviral clinical trial as a cornerstone for future metallodrug research. This review chronologically summarizes the synthesis (outline), structure, and anticancer property of the cobalt(II) and cobalt(III) Schiff base complexes and tried to gain insight into the biochemical and biophysical properties of these complexes that can be correlated further to improve the design of novel anticancer agents with better clinical applicability.
... Vitamin B12 is a water-soluble vitamin that acts as a cofactor in DNA synthesis, thus contributing to cell metabolism in the human body [11]. This vitamin is also essential for the normal function of the nervous system [12,13]. ...
Background: Multiple sclerosis (MS) is a chronic inflammatory demyelinating disorder of the central nervous system. It is an autoimmune disease of multifactorial etiology, linked to a variety of genetic and well-defined environmental factors. It typically affects more women than men and more frequently affects adults aged 20–45 years. Besides, vitamin B12 deficiency and obesity are associated with exacerbating central nervous system inflammation and a higher clinical disability. Objective: The study aims to determine the association of the vitamin B12 serum concentration with the Body Mass Index BMI, thyroid-stimulating hormone serum levels and MS clinical features in Saudi MS patients. Methods and results: This is a retrospective cohort study, and data were collected from the MS database at the King Fahad Medical City Multiple Sclerosis Clinic, from December 2015 to December 2019. Data were entered and analyzed using the Statistical Package for Social Sciences (SPSS ver. 20, Chicago, IL, USA). Cobalamin, also known as vitamin B12, has a reference concentration that ranges from 138 to 652 Pmol/L in adults. The patient's BMI was calculated by dividing the weight (in kilograms) by the square of the height (in square meters), expressed in kg/m2.Data for 169 MS subjects were collected. A total 83 of them, with a mean age of 36.2 ± 9.57 years, had vitamin B12 results. Of all patients, 16.6% had vitamin B12 deficiency (25). However, no significant correlation was found between vitamin B12 deficiency neither with the BMI nor TSH concentration in MS cases (r = 0.03, p = 0.64), (r = 0.00, P = 0.9) respectively. Conclusion: These findings revealed no association between serum vitamin B12 concentration and TSH, BMI in MS clinical parameters, however, further studies are required to validate these results.
The popularity of seafoods is high due to their superb dietary properties and healthy composition. However, it is crucial to understand whether they adequately contribute to our essential nutritional needs. Small amounts of essential metals are indispensable in the human body to proper physiological functioning; their deficiency can manifest in various sets of symptoms that can only be eliminated with their intake during treatment or nutrition. However, the excessive consumption of metals can induce undesirable effects, or even toxicosis. Shellfish, oyster, and squid samples were collected directly from a fish market. After sample preparation, the concentration of essential metals (cobalt, chromium, copper, manganese, molybdenum, nickel, and zinc) was detected by Inductively Coupled Plasma Optical Emission Spectrometry. The results were analyzed statistically using ANOVA and two-sample t-tests. The average concentration of the investigated essential elements and the calculated burden based on the consumption were below the Recommended Dietary Allowances and Tolerable Upper Intake Levels. Based on these results, the trace element contents of the investigated seafoods do not cover the necessary recommended daily intake of them, but their consumption poses no health hazard due to their low levels.
Immunoglobulin A nephropathy (IgAN) is the most common type of glomerulonephritis in adults worldwide. Environmental metal exposure has been reported to be involved in the pathogenic mechanisms of kidney diseases, yet no further epidemiological study has been conducted to assess the effects of metal mixture exposure on IgAN risk. In this study, we conducted a matched case‒control design with three controls for each patient to investigate the association between metal mixture exposure and IgAN risk. A total of 160 IgAN patients and 480 healthy controls were matched for age and sex. Plasma levels of arsenic, lead, chromium, manganese, cobalt, copper, zinc, and vanadium were measured using inductively coupled plasma mass spectrometry. We used a conditional logistic regression model to assess the association between individual metals and IgAN risk, and a weighted quantile sum (WQS) regression model to analyze the effects of metal mixtures on IgAN risk. Restricted cubic splines were used to evaluate overall associations between plasma metal concentrations and estimated glomerular filtration rate (eGFR) levels. We observed that except for Cu, all the metals analyzed were nonlinearly associated with decreased eGFR, and higher concentrations of arsenic and lead were associated with elevated IgAN risk in both single-metal [3.29 (1.94, 5.57), 6.10 (3.39, 11.0), respectively] and multiple-metal [3.04 (1.66, 5.57), 4.70 (2.47, 8.97), respectively] models. Elevated manganese [1.76 (1.09, 2.83)] levels were associated with increased IgAN risk in the single-metal model. Copper was inversely related to IgAN risk in both single-metal [0.392 (0.238, 0.645)] and multiple-metal [0.357 (0.200, 0.638)] models. The WQS indices in both positive [2.04 (1.68, 2.47)] and negative [0.717 (0.603, 0.852)] directions were associated with IgAN risk. Lead, arsenic, and vanadium contributed significant weights (0.594, 0.195, and 0.191, respectively) in the positive direction; copper, cobalt, and chromium carried significant weights (0.538, 0.253, and 0.209, respectively). In conclusion, metal exposure was related to IgAN risk. Lead, arsenic, and copper were all significantly weighted factors of IgAN development, which may require further investigation.
A series of copper(II), nickel(II) and cobalt(II) complexes with the non-steroidal anti-inflammatory drug oxaprozin (Hoxa) have been synthesized and characterized by diverse techniques. The crystal structures of two copper(II) complexes, namely the dinuclear complex [Cu2(oxa)4(DMF)2] (1) and the polymeric complex {[Cu2(oxa)4]·2MeOH·0.5MeOH}2 (12) were determined by single-crystal X-ray diffraction studies. In order to evaluate in vitro the antioxidant activity of the resultant complexes, their scavenging ability towards 1,1-diphenyl-picrylhydrazyl (DPPH), hydroxyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals was investigated revealing their high effectiveness against these radicals. The binding of the complexes to bovine serum albumin and human serum albumin was examined and the corresponding determined albumin-binding constants showed a tight and reversible interaction. The interaction of the complexes with calf-thymus DNA was monitored by diverse techniques including UV-vis spectroscopy, cyclic voltammetry, DNA-viscosity measurements and competitive studies with ethidium bromide. Intercalation may be proposed as the most possible DNA-interaction mode of the complexes.
Background: Diabetes mellitus is the most well-known endocrine disorder to date. Year after year, the prevalence of type 2 diabetes (T2D), which accounts for more than 90% of all diabetes cases, rises fast. Metformin is the most generally prescribed oral diabetes medication, and it is used to treat all diabetics worldwide in combination with diet and exercise. Though evidence shows that using metformin for a long time might cause vitamin B12 and folic acid deficiency, only a few studies have done in this regard. Materials and methods: Participants were divided into two groups: diabetic females (MET) (n = 60) and healthy control females (n = 25). All diabetic patients receiving Metformin (500 mg twice daily) were further divided into two groups based on treatment duration: less than 2 years and more than 2 years. Serum vitamin B12, folic acid, T3 and T4 levels were tested in the subjects. Results: the level of serum Folic acid in diabetic females with duration of metformin treatment more than 2 years was (77.05 ± 2.61), while its level in diabetic females with duration of metformin less than 2 years was (130.55 ± 1.86) both were significantly lower (p<0.001) than its level in healthy control (426.47 ± 32.51). Student's t-test demonstrated a very significant drop in blood folic acid levels in diabetic females who had used metformin for more than 2 years compared to females who had used metformin for less than 2 years. Conclustion : To determine the risk of B12 and B9 deficiency in Diabetes females taking metformin, compared to the healthy control group.
Drug resistance developed in microorganisms is a major concern which needs an immediate attention of the scientific community. Development of new drugs with different mode of actions is an effective...
Objective:
A high cobalamin level has been related to non-malignant diseases (mainly liver diseases, alcoholism, and renal diseases) and cancer (haematological malignancies and solid cancers such as liver and stomach cancer). However, a previous high level of cobalamin and the implications in the possible development of cancer is still unclear. The main objective of this study was to describe if a previous high cobalamin level is a determinant in the future development of cancer in five years of follow-up. The secondary objective was to determine any differences between cancer groups.
Methods:
A retrospective study was performed. Two databases were employed. The first one included all patients who had a determination of cobalamin in a routine blood test during the year 2010 (a total of 44,166 patients). The second one showed every patient who was admitted to the reference hospital, Hospital Clinico Universitario de Valladolid, during the following five years. Finally, a number of 6,710 patients was included. Both databases belong to the medical records of the Hospital Data Surveillance System, and are completely validated. Multivariate logistic regression analyses were employed to evaluate the association between cobalamin levels and the appearance of cancer (total and in each subgroup). All analyses were performed using IBM SPSS 24 software.
Results:
The sample studied showed a clear association between the risk of haematological cancer and a previous high Cbl level. This relationship was higher among patients with the highest levels (over 779 pmol/L), showing almost two times more risk for development of haematological malignance within 5 years in the multivariate analysis [OR: 1.975, 95% CI: 1.056-3.697, p=0.033]. Haematological malignancies were mostly diagnosed within the first three years (86.6%), showing a similar percentage in those three years. There was no association between this previous level and the development of any other type of cancer.
Conclusions:
Our study shows that a high cobalamin plasma level (hypervitaminosis) is associated with the development of haematologic cancer within five years after the measurement. The clinical implication of these findings, together with the clinical suspicion, reinforces the necessity of carrying out specific screening haematological tests in patients with not justified elevated plasma cobalamin levels. New prospective and multicentre studies are necessary in order to validate these results.
The reactivity and relative rarity of most cofactors pose challenges for their delivery to target enzymes. Using kinetic analyses, we demonstrate that adenosyltransferase, which catalyzes the final step in the assimilation of coenzyme B
An enzyme has been obtained from extracts of Escherichia coli which catalyzes the synthesis of N5-methyltetrahydrofolate-homocysteine methyltransferase holoenzyme from apoenzyme and 5,6-dimethylbenzimidazolylcobamide deoxyadenosyl
in the presence of a reduced pyridine nucleotide. In addition to holoenzyme formation, this system supplies the reducing power
for the synthesis of methionine from N5-methyl-H4-folate. It is suggested that this enzyme system functions by reducing the cobamide prosthetic group, and that it may be the
natural reducing system required for methionine synthesis in E. coli.
The mutation R403stop was found in an individual with mut0 methylmalonic aciduria (MMA) which resulted from a single base change of C→T in exon 6 of the methylmalonyl-CoA mutase gene (producing a TGA stop codon). In order to accurately model the human MMA disorder we introduced this mutation onto the human methylmalonyl-CoA mutase locus of a bacterial artificial chromosome. A mouse model was developed using this construct.
The transgene was found to be intact in the mouse model, with 7 copies integrated at a single site in chromosome 3. The phenotype of the hemizygous mouse was unchanged until crossed against a methylmalonyl-CoA mutase knockout mouse. Pups with no endogenous mouse methylmalonyl-CoA mutase and one copy of the transgene became ill and died within 24 hours. This severe phenotype could be partially rescued by the addition of a transgene carrying two copies of the normal human methylmalonyl-CoA mutase locus. The “humanized” mice were smaller than control litter mates and had high levels of methylmalonic acid in their blood and tissues.
This new transgenic MMA stop codon model mimics (at both the phenotypic and genotypic levels) the key features of the human MMA disorder. It will allow the trialing of pharmacological and, cell and gene therapies for the treatment of MMA and other human metabolic disorders caused by stop codon mutations.
Inherited disorders of vitamin B(12) (cobalamin) have provided important clues to how this vitamin, which is essential for hematological and neurological function, is transported and metabolized. We describe a new disease that results in failure to release vitamin B(12) from lysosomes, which mimics the cblF defect caused by LMBRD1 mutations. Using microcell-mediated chromosome transfer and exome sequencing, we identified causal mutations in ABCD4, a gene that codes for an ABC transporter, which was previously thought to have peroxisomal localization and function. Our results show that ABCD4 colocalizes with the lysosomal proteins LAMP1 and LMBD1, the latter of which is deficient in the cblF defect. Furthermore, we show that mutations altering the putative ATPase domain of ABCD4 affect its function, suggesting that the ATPase activity of ABCD4 may be involved in intracellular processing of vitamin B(12).
Background:
Nitrile hydratases are enzymes involved in the conversion of nitrile-containing compounds into ammonia and organic acids. Although they are widespread in prokaryotes, nitrile hydratases have only been reported in two eukaryotes: the choanoflagellate Monosiga brevicollis and the stramenopile Aureococcus anophagefferens. The nitrile hydratase gene in M. brevicollis was believed to have arisen by lateral gene transfer from a prokaryote, and is a fusion of beta and alpha nitrile hydratase subunits. Only the alpha subunit has been reported in A. anophagefferens.
Methodology/principal findings:
Here we report the detection of nitrile hydratase genes in five eukaryotic supergroups: opisthokonts, amoebozoa, archaeplastids, CCTH and SAR. Beta-alpha subunit fusion genes are found in the choanoflagellates, ichthyosporeans, apusozoans, haptophytes, rhizarians and stramenopiles, and potentially also in the amoebozoans. An individual alpha subunit is found in a dinoflagellate and an individual beta subunit is found in a haptophyte. Phylogenetic analyses recover a clade of eukaryotic-type nitrile hydratases in the Opisthokonta, Amoebozoa, SAR and CCTH; this is supported by analyses of introns and gene architecture. Two nitrile hydratase sequences from an animal and a plant resolve in the prokaryotic nitrile hydratase clade.
Conclusions/significance:
The evidence presented here demonstrates that nitrile hydratase genes are present in multiple eukaryotic supergroups, suggesting that a subunit fusion gene was present in the last common ancestor of all eukaryotes. The absence of nitrile hydratase from several sequenced species indicates that subunits were lost in multiple eukaryotic taxa. The presence of nitrile hydratases in many other eukaryotic groups is unresolved due to insufficient data and taxon sampling. The retention and expression of the gene in distantly related eukaryotic species suggests that it plays an important metabolic role. The novel family of eukaryotic nitrile hydratases presented in this paper represents a promising candidate for research into their molecular biology and possible biotechnological applications.
Moderately elevated blood levels of homocysteine are weakly correlated with coronary heart disease (CHD) risk, but causality remains uncertain. When folate levels are low, the TT genotype of the common C677T polymorphism (rs1801133) of the methylene tetrahydrofolate reductase gene (MTHFR) appreciably increases homocysteine levels, so "Mendelian randomization" studies using this variant as an instrumental variable could help test causality.
Nineteen unpublished datasets were obtained (total 48,175 CHD cases and 67,961 controls) in which multiple genetic variants had been measured, including MTHFR C677T. These datasets did not include measurements of blood homocysteine, but homocysteine levels would be expected to be about 20% higher with TT than with CC genotype in the populations studied. In meta-analyses of these unpublished datasets, the case-control CHD odds ratio (OR) and 95% CI comparing TT versus CC homozygotes was 1.02 (0.98-1.07; p = 0.28) overall, and 1.01 (0.95-1.07) in unsupplemented low-folate populations. By contrast, in a slightly updated meta-analysis of the 86 published studies (28,617 CHD cases and 41,857 controls), the OR was 1.15 (1.09-1.21), significantly discrepant (p = 0.001) with the OR in the unpublished datasets. Within the meta-analysis of published studies, the OR was 1.12 (1.04-1.21) in the 14 larger studies (those with variance of log OR<0.05; total 13,119 cases) and 1.18 (1.09-1.28) in the 72 smaller ones (total 15,498 cases).
The CI for the overall result from large unpublished datasets shows lifelong moderate homocysteine elevation has little or no effect on CHD. The discrepant overall result from previously published studies reflects publication bias or methodological problems.
Methionine synthase catalyzes the remethylation of homocysteine to methionine via a reaction in which methylcobalamin serves as an intermediate methyl carrier. Over time, the cob(I)alamin cofactor of methionine synthase becomes oxidized to cob(II)alamin rendering the enzyme inactive. Regeneration of functional enzyme requires reductive methylation via a reaction in which S-adenosylmethionine is utilized as a methyl donor. Patients of the cblE complementation group of disorders of folate/cobalamin metabolism who are defective in reductive activation of methionine synthase exhibit megaloblastic anemia, developmental delay, hyperhomocysteinemia, and hypomethioninemia. Using consensus sequences to predicted binding sites for FMN, FAD, and NADPH, we have cloned a cDNA corresponding to the "methionine synthase reductase" reducing system required for maintenance of the methionine synthase in a functional state. The gene MTRR has been localized to chromosome 5p15.2-15.3. A predominant mRNA of 3.6 kb is detected by Northern blot analysis. The deduced protein is a novel member of the FNR family of electron transferases, containing 698 amino acids with a predicted molecular mass of 77,700. It shares 38% identity with human cytochrome P450 reductase and 43% with the C. elegans putative methionine synthase reductase. The authenticity of the cDNA sequence was confirmed by identification of mutations in cblE patients, including a 4-bp frameshift in two affected siblings and a 3-bp deletion in a third patient. The cloning of the cDNA will permit the diagnostic characterization of cblE patients and investigation of the potential role of polymorphisms of this enzyme as a risk factor in hyperhomocysteinemia-linked vascular disease.
An early step in the intracellular processing of vitamin B(12) involves CblC, which exhibits dual reactivity, catalyzing the reductive decyanation of cyanocobalamin (vitamin B(12)), and the dealkylation of alkylcobalamins (e.g. methylcobalamin; MeCbl). Insights into how the CblC scaffold supports this chemical dichotomy have been unavailable despite it being the most common locus of patient mutations associated with inherited cobalamin disorders that manifest in both severe homocystinuria and methylmalonic aciduria. Herein, we report structures of human CblC, with and without bound MeCbl, which provide novel biochemical insights into its mechanism of action. Our results reveal that CblC is the most divergent member of the NADPH-dependent flavin reductase family and can use FMN or FAD as a prosthetic group to catalyze reductive decyanation. Furthermore, CblC is the first example of an enzyme with glutathione transferase activity that has a sequence and structure unrelated to the GST superfamily. CblC thus represents an example of evolutionary adaptation of a common structural platform to perform diverse chemistries. The CblC structure allows us to rationalize the biochemical basis of a number of pathological mutations associated with severe clinical phenotypes.
To the editor:
Recently, Beedholm-Ebsen and colleagues reported that the ABCC1 gene is involved in the efflux of cobalamin (Cbl; vitamin B12) from the enterocytes and other cells to the plasma.[1][1] ABCC1 encodes the multidrug resistance protein 1 (MRP1), a member of the ATP-binding cassette (ABC
This chapter reviews the literature on cobalamin- and corrinoid-containing enzymes. These enzymes fall into two broad classes, those using methylcobalamin or related methylcorrinoids as prosthetic groups and catalyzing methyl transfer reactions, and those using adenosylcobalamin as the prosthetic group and catalyzing the generation of substrate radicals that in turn undergo rearrangements and/or eliminations.
Vitamin B(12) (cobalamin, Cbl) is essential to the function of two human enzymes, methionine synthase (MS) and methylmalonyl-CoA mutase (MUT). The conversion of dietary Cbl to its cofactor forms, methyl-Cbl (MeCbl) for MS and adenosyl-Cbl (AdoCbl) for MUT, located in the cytosol and mitochondria, respectively, requires a complex pathway of intracellular processing and trafficking. One of the processing proteins, MMAA (methylmalonic aciduria type A), is implicated in the mitochondrial assembly of AdoCbl into MUT and is defective in children from the cblA complementation group of cobalamin disorders. To characterize the functional interplay between MMAA and MUT, we have crystallized human MMAA in the GDP-bound form and human MUT in the apo, holo, and substrate-bound ternary forms. Structures of both proteins reveal highly conserved domain architecture and catalytic machinery for ligand binding, yet they show substantially different dimeric assembly and interaction, compared with their bacterial counterparts. We show that MMAA exhibits GTPase activity that is modulated by MUT and that the two proteins interact in vitro and in vivo. Formation of a stable MMAA-MUT complex is nucleotide-selective for MMAA (GMPPNP over GDP) and apoenzyme-dependent for MUT. The physiological importance of this interaction is highlighted by a recently identified homoallelic patient mutation of MMAA, G188R, which, we show, retains basal GTPase activity but has abrogated interaction. Together, our data point to a gatekeeping role for MMAA by favoring complex formation with MUT apoenzyme for AdoCbl assembly and releasing the AdoCbl-loaded holoenzyme from the complex, in a GTP-dependent manner.
The mechanism by which docking fidelity is achieved for the multitude of cofactor-dependent enzymes is poorly understood. In this study, we demonstrate that delivery of coenzyme B(12) or 5'-deoxyadenosylcobalamin by adenosyltransferase to methylmalonyl-CoA mutase is gated by a small G protein, MeaB. While the GTP-binding energy is needed for the editing function; that is, to discriminate between active and inactive cofactor forms, the chemical energy of GTP hydrolysis is required for gating cofactor transfer. The G protein chaperone also exerts its editing function during turnover by using the binding energy of GTP to elicit release of inactive cofactor that is occasionally formed during the catalytic cycle of MCM. The physiological relevance of this mechanism is demonstrated by a patient mutation in methylmalonyl-CoA mutase that does not impair the activity of this enzyme per se but corrupts both the fidelity of the cofactor-loading process and the ejection of inactive cofactor that forms occasionally during catalysis. Consequently, cofactor in the incorrect oxidation state gains access to the mutase active site and is not released if generated during catalysis, leading, respectively, to assembly and accumulation of inactive enzyme and resulting in methylmalonic aciduria.
Cobalamin (Cbl, vitamin B(12)) deficiency in humans is a cause of hematologic and neurologic disorders. We show here that the cellular export of Cbl, in contrast to the carrier- and receptor-dependent cellular import of Cbl, occurs by transmembrane transport of "free" Cbl. Screening of candidate transporters by cellular gene silencing showed a role in cellular Cbl efflux of the ATP-binding cassette (ABC)-drug transporter, ABCC1, alias multidrug resistance protein 1 (MRP1), which is present in the basolateral membrane of intestinal epithelium and in other cells. The ability of MRP1 to mediate ATP-dependent Cbl transport was confirmed by vesicular transport experiments, and a physiologic role of MRP1 in mammalian Cbl homeostasis is indicated by the phenotype of knockout mice with targeted disruption of MRP1. These animals have a reduced concentration of Cbl in plasma and in the storage organs liver and kidney. In contrast, Cbl accumulates in the terminal part of the intestine of these mice, suggesting a functional malabsorption because of a lower epithelial basolateral Cbl efflux. The identification of this Cbl export mechanism now allows the delineation of a coherent pathway for Cbl trafficking from food to the body cells.
Alterations in homocysteine, methionine, folate, and/or B12 homeostasis have been associated with neural tube defects, cardiovascular disease, and cancer. Methionine synthase, one of only two mammalian enzymes known to require vitamin B12 as a cofactor, lies at the intersection of these metabolic pathways. This enzyme catalyzes the transfer of a methyl group from 5-methyl-tetrahydrofolate to homocysteine, generating tetrahydrofolate and methionine. Human patients with methionine synthase deficiency exhibit homocysteinemia, homocysteinuria, and hypomethioninemia. They suffer from megaloblastic anemia with or without some degree of neural dysfunction and mental retardation. To better study the pathophysiology of methionine synthase deficiency, we utilized gene-targeting technology to inactivate the methionine synthase gene in mice. On average, heterozygous knockout mice from an outbred background have slightly elevated plasma homocysteine and methionine compared to wild-type mice but seem to be otherwise indistinguishable. Homozygous knockout embryos survive through implantation but die soon thereafter. Nutritional supplementation during pregnancy was unable to rescue embryos that were completely deficient in methionine synthase. Whether any human patients with methionine synthase deficiency have a complete absence of enzyme activity is unclear. These results demonstrate the importance of this enzyme for early development in mice and suggest either that methionine synthase-deficient patients have residual methionine synthase activity or that humans have a compensatory mechanism that is absent in mice.
Vitamin B(12) (cobalamin) is essential in animals for metabolism of branched chain amino acids and odd chain fatty acids, and for remethylation of homocysteine to methionine. In the cblF inborn error of vitamin B(12) metabolism, free vitamin accumulates in lysosomes, thus hindering its conversion to cofactors. Using homozygosity mapping in 12 unrelated cblF individuals and microcell-mediated chromosome transfer, we identified a candidate gene on chromosome 6q13, LMBRD1, encoding LMBD1, a lysosomal membrane protein with homology to lipocalin membrane receptor LIMR. We identified five different frameshift mutations in LMBRD1 resulting in loss of LMBD1 function, with 18 of the 24 disease chromosomes carrying the same mutation embedded in a common 1.34-Mb haplotype. Transfection of fibroblasts of individuals with cblF with wild-type LMBD1 rescued cobalamin coenzyme synthesis and function. This work identifies LMBRD1 as the gene underlying the cblF defect of cobalamin metabolism and suggests that LMBD1 is a lysosomal membrane exporter for cobalamin.
Bacterial nitrile hydratase (NHases) are important industrial catalysts and waste water remediation tools. In a global computational screening of conventional and metagenomic sequence data for NHases, we detected the two usually separated NHase subunits fused in one protein of the choanoflagellate Monosiga brevicollis, a recently sequenced unicellular model organism from the closest sister group of Metazoa. This is the first time that an NHase is found in eukaryotes and the first time it is observed as a fusion protein. The presence of an intron, subunit fusion and expressed sequence tags covering parts of the gene exclude contamination and suggest a functional gene. Phylogenetic analyses and genomic context imply a probable ancient horizontal gene transfer (HGT) from proteobacteria. The newly discovered NHase might open biotechnological routes due to its unconventional structure, its new type of host and its apparent integration into eukaryotic protein networks.
We identified previously an intracellular cobalamin (Cbl) binding protein(s) in cultured human fibroblasts, distinct from known Cbl "R" binders and absent from mutant cells deficient in the synthesis of the two Cbl coenzymes. In order to further characterize this binding activity, we have investigated its homologue in rat liver. After being transported to the liver by the serum protein transcobalamin II, [57Co]Cbl was bound by at least two distinct proteins, one cytosolic, the other mitochondrial. Labeled Cbl bound to cytosolic protein faster than or prior to the mitochondrial protein. With time there was a decline in radioactivity associated with the cytosolic binder and a coordinate increase in that associated with the mitochondrial binder. Although both proteins cochromatographed on Sephadex G-150 and had apparent molecular weights of 120,000, they were separated into two discrete components by polyacrylamide gel electrophoresis and by DEAE-cellulose chromatography. The cytosolic binder cochromatographed with N5-methyltetrahydrofolate:homocysteine methyltransferase activity (5-methyltetrahydropteroyl-L-glutamate:L-homocysteine S-methyltransferase, EC 2.1.1.13); the mitochondrial one with methylmalonyl CoA mutase activity (methylmalonyl-CoA CoA-carbonylmutase, EC 5.4.99.2). These proteins were distinguished further by the chemical forms of [57Co]Cbl found with them, hydroxocobalamin and methylcobalamin with the cytosolic protein and adenosylcobalamin with the mitochondrial one. These results suggest that intracellular Cbl binding activity in rat liver can be accounted for by attachment of Cbl to the two known Cbl-dependent apoenzymes, methylmalonyl CoA mutase and methyltetrahydrofolate methyltransferase. The mechanism and significance of the observered binding protein deficiency in mutant human fibroblasts must, therefore, be re-evaluated.
A methionine aminopeptidase that specifically removes methionine residues from peptides with amino-terminal sequences of Met-Ala-, Met-Val-, Met-Ser-, Met-Gly-, and Met-Pro- but not Met-Leu- or Met-Lys-has been isolated to homogeneity from porcine liver by a procedure involving five chromatographic steps. The enzyme, whose specificity matches that predicted for the entity responsible for the co-translational amino-terminal processing of nascent polypeptide chains, has a measured molecular mass of 70,000 Da by SDS-polyacrylamide electrophoresis and 67,000 Da by gel chromatography (under nondenaturing conditions), suggesting the native molecule is a monomer. It is activated by Co2+ and inhibited by β-mercaptoethanol and EDTA. With octapeptide substrates related to the amino-terminal portion of the β-chain of human hemoglobin (with a histidine in position 3), the enzyme had a pH optimum of 6.0. With a synthetic peptide devoid of histidine, it showed no pH dependence from 6.0 to 8.0. This sensitivity may be due to the propensity of peptides with histidine in the third position to bind divalent cations such as Co2+. The measured Km and kcat values were affected by residues in the second position. The peptide corresponding to the natural sequence (Met-Val-His-) gave a kcat/Km value of 260 mM-1 s-1; substitution of alanine in the second position raised the kcat/Km to 1523 mM-1 s-1, but substitution of proline lowered the value to 130. The effects are primarily on the kcat. The substitution of proline (for histidine) in the third position, the mutation found in hemoglobin Long Island, prevents the removal of the methionine residue, as occurs with the mutant protein. The porcine liver enzyme is similar to methionine aminopeptidases isolated from Escherichia coli, Salmonella typhimurium, and yeast in that it also is stimulated by Co2+. However, it is much larger than these enzymes and differs somewhat in specificity, particularly with the yeast enzyme.
The changes in the activities of the two vitamin B12-dependent enzymes methylmalonyl-CoA mutase (EC 5.4.99.2) and methionine synthetase (5-methyltetrahydrofolate-homocysteine methyltransferase, EC 2.1.1.13) are described in two groups of sheep maintained for 20 weeks on either a cobalt-deficient or a Co-sufficient whole-barley diet. At the end of that period, the plasma concentrations of vitamin B12 were depressed and those of methylmalonic acid were raised in the Co-deficient group. During the course of the experiment hepatic holo-mutase activity, measured on biopsy samples, declined in Co-deficient animals with a half-life of 73 d. There was a similar, but slower decline in lymphocyte holo-mutase activity which fell with a half-life of 125 d. At slaughter, there was no difference between Co-sufficient and Co-deficient animals in total mutase activity in liver, kidney, brain and spinal cord. In contrast, the total-synthetase activity of liver and kidney was reduced by 60 and 30% respectively in the Co-deficient animals. There was no change in either group of animals in total-synthetase activity, or in either holo-mutase or holo-synthetase activity, in brain and spinal cord. In the Co-deficient animals, holo-mutase and holo-synthetase activities in liver, the tissue with the greatest activity of both enzymes, fell to 25 and 39% respectively, of that of Co-sufficient animals. The corresponding reductions for kidney were 12 and 51% respectively. These results indicated that activity of both holoenzymes is greatly reduced in Co-deficient sheep.
Vitamin B12 (VB12) was administered to two patients suffering for many years from different sleep-wake rhythm disorders. One patient was a 15-year-old blind girl suffering from a free-running sleep-wake rhythm (hypernychthemeral syndrome) with a period of about 25 h. In spite of repeated trials to entrain her sleep-wake cycle to the environmental 24-h rhythm, her free-running rhythm persisted for about 13 years. When she was 14 years old, administration of VB12 per os was started at the daily dose of 1.5 mg t.i.d. Shortly thereafter, her sleep-wake rhythm was entrained to the environmental 24-h rhythm, and her 24-h sleep-wake rhythm was maintained while she was on the medication. Within 2 months of the withholding of VB12, her free-running sleep-wake rhythm reappeared. The VB12 level in the serum was within the normal range both before and after treatment. The other patient was a 55-year-old man suffering from delayed sleep phase syndrome since 18 years of age. After administration of VB12 at the daily doses of 1.5 mg, his sleep-wake rhythm disorder was improved. The good therapeutic effect lasted for more than 6 months while he was on the medication.
The serum cobalamin level has been generally considered to be essentially 100% sensitive in the detection of the clinical disorders caused by cobalamin deficiency. We tested this hypothesis in two groups of patients. In patients with pernicious anemia or previous gastrectomy who received less than monthly maintenance therapy, early hematologic relapse was associated with elevation of the serum methylmalonic acid, total homocysteine, or both metabolites in 95% of instances, although the serum cobalamin was low in only 69%. In the absence of hematologic relapse, the methylmalonic acid was abnormal more than twice as frequently as the serum cobalamin. We also reviewed the records of 419 consecutive patients with recognized clinically significant cobalamin deficiency. Twelve patients were identified in whom deficiency was clearly present although the serum cobalamin was greater than 200 pg/ml. Anemia was usually absent or mild, but 5 had prominent neurological involvement that subsequently responded to cobalamin. Both the serum methylmalonic acid and total homocysteine were increased in each patient. The serum cobalamin was normal in 9 (5.2%) of 173 patients with recognized cobalamin deficiency seen in the last 5 years. Antibiotic treatment lowered the serum methylmalonic acid but not the total homocysteine level in two cobalamin-deficient patients, suggesting that propionic acid generated by the anaerobic gut flora may be a precursor of methylmalonic acid in deficient patients. We conclude that the serum cobalamin is normal in a significant minority of patients with cobalamin deficiency and that the measurement of serum metabolite concentrations facilitates the identification of such patients.
A gene encoding cobalamin-dependent methionine synthase (EC 2.1.1.13) has been isolated from a plasmid library of Escherichia coli K-12 DNA by complementation to methionine prototrophy in an E. coli strain lacking both cobalamin-dependent and -independent methionine synthase activities (RK4536:metE, metHH). Maxicell expression of a series of plasmids containing deletions in the metH structural gene was employed to map the position and orientation of the gene on the cloned DNA fragment. A 6.3-kilobase EcoRI-SalI fragment containing the gene was cloned into the sequencing vector pGEM3B for double-stranded DNA sequencing; the MetH coding region consists of 3372 nucleotides. The enzyme was purified from an overproducing strain of E. coli harboring the recombinant plasmid, in which the level of methionine synthase was elevated 30- to 40-fold over wild-type E. coli. Recombinant enzyme is a protein of 123,640 molecular weight and has a turnover number of 1,450 min-1 in the standard assay. These values are to be compared with previously reported values of 133,000 for the molecular weight and 1,240-1,560 min-1 for the turnover number of the homogenous enzyme purified from a wild-type strain of E. coli B (Frasca, V., Banerjee, R. V., Dunham, W. R., Sands, R. H., and Matthews, R. G. (1988) Biochemistry 27, 8458-8465). Limited proteolysis of the native enzyme with trypsin resulted in loss of enzyme activity but retention of bound cobalamin on a peptide fragment of 28,000 molecular weight. This fragment has been shown to extend from residue 643 to residue 900 of the 1124-residue deduced amino acid sequence.
Nitrous oxide (N2O) is commonly used as an anesthetic agent. Prolonged exposure to N2O leads to megaloblastic anemia in humans and to loss of methionine synthase activity in vertebrates. We now report that purified preparations of cobalamin-dependent methionine synthase (5-methyltetrahydrofolate-homocysteine methyltransferase, EC 2.1.1.13) from both Escherichia coli and pig liver are irreversibly inactivated during turnover in buffers saturated with N2O. Inactivation by N2O occurs only in the presence of all components required for turnover: homocysteine, methyltetrahydrofolate, adenosylmethionine, and a reducing system. Reisolation of the inactivated E. coli enzyme after turnover in the presence of N2O resulted in significant losses of bound cobalamin and of protein as compared to controls where the enzyme was subjected to turnover in N2-equilibrated buffers before reisolation. However, N2O inactivation was not associated with major changes in the visible absorbance spectrum of the remaining enzyme-bound cobalamin. We postulate that N2O acts by one-electron oxidation of the cob(I)alamin form of the enzyme which is generated transiently during turnover with the formation of cob(II)alamin, N2, and hydroxyl radical. Generation of hydroxyl radical at the active site of the enzyme could explain the observed irreversible loss of enzyme activity.
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The occurrence of a wide variety of metal-carbon bonds in living organisms, ranging from bacteria to humans, is only recently recognized. Of course, the historical examples are the B12 coenzymes containing cobalt-carbon bonds, but now such bonds are also known for nickel, iron, copper, and other transition metal ions. There is no other comparable book; MILS-6, written by 17 experts, summarizes the most recent insights into this fascinating topic.
To elucidate the biochemical basis of megaloblastic hematopoiesis, the cellular content and metabolism of deoxyribonucleoside triphosphates (dNTPs) were investigated using the bone marrow cells from nine patients with untreated vitamin B12 deficiency and one with folic acid deficiency. The marked imbalance among four dNTPs was noted in all patients. dTTP was invariably elevated rather than depressed. The most striking abnormality, however, was the excessive accumulation of dCTP, which represented the consistent feature exclusive for megaloblastic anemia. Purine nucleotides were also involved to a lesser extent. The apparent turnover pattern of the dTTP pool of megaloblastic anemia marrow cells, in the presence or absence of hydroxyurea, did not differ significantly from that of normoblastic hematopoiesis. The megaloblastic cells assimilated exogenous thymidine into dTTP pool in vitro with enhanced efficiency. It was suggested that the excessive accumulation of dCTP may be related more closely to the pathogenesis of megaloblastic hematopoiesis than to the presumed but not proved deficiency of dTTP.
The methylmalonic acidurias are metabolic disorders resulting from deficient methylmalonyl-CoA mutase activity, a vitamin B 12 -dependent enzyme. We have cloned the gene for the cblB complementation group caused by deficient activity of a cob(I)alamin adenosyltransferase. This was accomplished by searching bacterial genomes for genes in close proximity to the methylmalonyl-CoA mutase gene that might encode a protein with the properties of an adenosyltransferase. A candidate was identified in the Archaeoglobus fulgidus genome and was used to probe the human genome database. It yielded a gene on chromosome 12q24 that encodes a predicted protein of 250 amino acids with 45% similarity to PduO in Salmonella enterica, a characterized cob(I)alamin adenosyltransferase. A northern blot revealed an RNA species of 1.1 kb predominating in liver and skeletal muscle. The gene was evaluated for deleterious mutations in cblB patient cell lines. Several mutations were identified including a 5bp deletion (5del572gggcc576), two splice site mutations (IVS2-1G>T, IVS3-1G>A), andt several point mutations (A135T, R186W, R191W and E193K). Two additional amino acid substitutions (R19Q and M239K) were found in several patient cell lines but were found to be common polymorphisms (36% and 46%) in control alleles. The R186W mutation, which we suggest is disease-linked, is present in four of the six patient cell lines examined (homoallelic in two) and in 4 of 240 alleles in control samples. These data confirm that the identified gene, MMAB, corresponds to the cblB complementation group and has the appearance of a cob(I)alamin adenosyltransferase, as predicted from biochemical data.
The purpose of this review is to summarise the data concerning genotoxicity and carcinogenicity of Co and Sb. Both metals have multiple industrial and/or therapeutical applications, depending on the considered species. Cobalt is used for the production of alloys and hard metal (cemented carbide), diamond polishing, drying agents, pigments and catalysts. Occupational exposure to cobalt may result in adverse health effects in different organs or tissues. Antimony trioxide is primarily used as a flame retardant in rubber, plastics, pigments, adhesives, textiles, and paper. Antimony potassium tartrate has been used worldwide as an anti-shistosomal drug. Pentavalent antimony compounds have been used for the treatment of leishmaniasis. Co(II) ions are genotoxic in vitro and in vivo, and carcinogenic in rodents. Co metal is genotoxic in vitro. Hard metal dust, of which occupational exposure is linked to an increased lung cancer risk, is proven to be genotoxic in vitro and in vivo. Possibly, production of active oxygen species and/or DNA repair inhibition are mechanisms involved. Given the recently provided proof for in vitro and in vivo genotoxic potential of hard metal dust, the mechanistic evidence of elevated production of active oxygen species and the epidemiological data on increased cancer risk, it may be advisable to consider the possibility of a new evaluation by IARC. Both trivalent and pentavalent antimony compounds are generally negative in non-mammalian genotoxicity tests, while mammalian test systems usually give positive results for Sb(III) and negative results for Sb(V) compounds. Assessment of the in vivo potential of Sb2O3 to induce chromosome aberrations (CA) gave conflicting results. Animal carcinogenicity data were concluded sufficient for Sb2O3 by IARC. Human carcinogenicity data is difficult to evaluate given the frequent co-exposure to arsenic. Possible mechanisms of action, including potential to produce active oxygen species and to interfere with DNA repair systems, still need further investigation.
The mechanism of reactivation of diol dehydratase by its reactivating factor was investigated in vitro by using enzyme cyanocobalamin complex as a model for inactivated holoenzyme. The factor mediated the exchange of the enzyme-bound, adenine-lacking cobalamins for Tree, adenine-containing cobalamins through intermediate formation of apoenzyme. The factor showed extremely low but distinct ATP-hydrolyzing activity. It formed a tight complex with apoenzyme in the presence of ADP but not at all in the presence of ATP. Incubation of the enzyme cyanocobalamin complex with the reactivating factor in the presence of ADP brought about release of the enzyme-bound cobalamin, leaving the tight apoenzyme-reactivating factor complex. Although the resulting complex was inactive even in the presence of added adenosylcobalamin, it dissociated by incubation with ATP, forming the apoenzyme, which was reconstitutable into active holoenzyme with added coenzyme. Thus, it was established that the reactivation of the inactivated holoenzyme by the factor in the presence of ATP and Mg2+ takes place in two steps: ADP-dependent cobalamin release and ATP-dependent dissociation of the apoenzyme factor complex. ATP plays dual roles as a precursor of ADP in the first step and as an effector to change the factor into the low-affinity form for diol dehydratase. The enzyme-bound adenosylcobalamin was also susceptible to exchange with free adeninylpentylcobalamin, although to a much lesser degree. The mechanism for discrimination of adenine-containing cobalamins from adenine-lacking cobalamins was explained in terms of formation equilibrium constants of the cobalamin enzyme reactivating factor ternary complexes. We propose that the reactivating factor is a new type of molecular chaperone that participates in reactivation of the inactivated enzymes.
Aim:
A novel biomimetic strategy was employed for presenting antibodies on gold nanorods (NRs) to target growth factor receptors on cancer cells for use in photothermal therapy.
Materials & methods:
Polydopamine (PD) was polymerized onto gold NRs, and EGF receptor antibodies (anti-EGFR) were immobilized onto the layer. Cell-binding affinity and light-activated cell death of cancer cells incubated with anti-EGFR-PD-NRs were quantified by optical imaging.
Results:
PD was deposited onto gold NRs, and antibodies were bound to PD-coated NRs. Anti-EGFR-PD-NRs were stable in media, and were specifically bound to EGFR-overexpressing cells. Illumination of cells targeted with anti-EGFR-PD-NRs enhanced cell death compared with nonirradiated controls and cells treated with antibody-free NRs.
Conclusion:
PD facilitates the surface functionalization of gold NRs with biomolecules, allowing cell targeting and photothermal killing of cancer cells. PD can potentially coat a large variety of nanoparticles with targeting ligands as a strategy for biofunctionalization of diagnostic and therapeutic nanoparticles.
The binding of several corrinoids to the binding site of human intrinsic factor, transcobalamin or haptocorrin was investigated. p ‐Cresolyl cobamide and 2‐amino‐vitamin B 12 are complete corrinoids, whose nucleotide at the lower face of the corrin ring is not coordinated to the cobalt. These corrinoids were ≥ 10 ³ times less efficiently recognized by intrinsic factor or transcobalamin than vitamin B 12 , which contains a Co‐coordinated nucleotide. Pseudovitamin B 12 , with a weak Co‐N coordination bond, revealed only moderate affinity to intrinsic factor. From these findings it is concluded that the cobamide binding to intrinsic factor and transcobalamin is strongly affected by the Co‐N coordination bonds of their lower cobalt nucleotide ligands. We suggest that the Co‐N coordination bond positions the nucleotide at a critical distance to the corrin ring, which is recognized by the binding proteins.
Human haptocorrin, however, disclosed to distinctive selectivity regarding the different corrinoid structures. The protein bound all corrinoids with similar efficiency, independent of the strength of their Co‐N coordinations, or the structures of their lower Coα ligands. Hence, the corrin ring, rather than a structural feature induced by the Co‐N coordination, has to be considered responsible for the corrinoid binding to haptocorrin.
Adenosylcobalamin‐dependent diol dehydratase (DD) undergoes suicide inactivation by glycerol, one of its physiological substrates, resulting in the irreversible cleavage of the coenzyme Co–C bond. The damaged cofactor remains tightly bound to the active site. The DD‐reactivating factor reactivates the inactivated holoenzyme in the presence of ATP and Mg ²⁺ by mediating the exchange of the tightly bound damaged cofactor for free intact coenzyme. In this study, we demonstrated that this reactivating factor mediates the cobalamin exchange not stoichiometrically but catalytically in the presence of ATP and Mg ²⁺ . Therefore, we concluded that the reactivating factor is a sort of enzyme. It can be designated DD reactivase. The reactivase showed broad specificity for nucleoside triphosphates in the activation of the enzyme·cyanocobalamin complex. This result is consistent with the lack of specific interaction with the adenine ring of ADP in the crystal structure of the reactivase. The specificities of the reactivase for divalent metal ions were also not strict. DD formed 1 : 1 and 1 : 2 complexes with the reactivase in the presence of ADP and Mg ²⁺ . Upon complex formation, one β subunit was released from the (αβ) 2 tetramer of the reactivase. This result, together with the similarity in amino acid sequences and folds between the DD β subunit and the reactivase β subunit, suggests that subunit displacement or swapping takes place upon formation of the enzyme·reactivase complex. This would result in the dissociation of the damaged cofactor from the inactivated holoenzyme, as suggested by the crystal structures of the reactivase and DD.
Structured digital abstract
MINT‐7997177 : Reactivase alpha (uniprotkb: O68195 ), Reactivase beta (uniprotkb: O68196 ), Diol Dehydratase gamma (uniprotkb: Q59472 ), Diol Dehydratase beta (uniprotkb: Q59471 ) and Diol Dehydratase alpha (uniprotkb: Q59470 ) physically interact ( MI:0915 ) by comigration in non denaturing gel electrophoresis ( MI:0404 )
MINT‐7997157 : Diol Dehydratase alpha (uniprotkb: Q59470 ), Diol Dehydratase beta (uniprotkb: Q59471 ), Diol Dehydratase gamma (uniprotkb: Q59472 ), Reactivase beta (uniprotkb: O68196 ) and Reactivase alpha (uniprotkb: O68195 ) physically interact ( MI:0915 ) by molecular sieving ( MI:0071 )
Human methionine synthase reductase (MSR), a diflavin enzyme, restores the activity of human methionine synthase through reductive methylation of methionine synthase (MS)-bound cob(II)alamin. Recently, it was also reported that MSR enhances uptake of cobalamin by apo-MS, a role associated with the MSR-catalysed reduction of exogenous aquacob(III)alamin to cob(II)alamin [Yamada K, Gravel RA, TorayaT & Matthews RG (2006) Proc Natl Acad Sci USA103, 9476-9481]. Here, we report the expression and purification of human methionine synthase from Pichia pastoris. This has enabled us to assess the ability of human MSR and two other structurally related diflavin reductase enzymes (cytochrome P450 reductase and the reductase domain of neuronal nitric oxide synthase) to: (a) stimulate formation of holo-MS from aquacob(III)alamin and the apo-form of MS; and (b) reactivate the inert cob(II)alamin form of MS that accumulates during enzyme catalysis. Of the three diflavin reductases studied, cytochrome P450 reductase had the highest turnover rate (55.5 s(-1)) for aquacob(III)alamin reduction, and the reductase domain of neuronal nitric oxide synthase elicited the highest specificity (k(cat)/K(m) of 1.5 x 10(5) m(-1) s(-1)) and MSR had the lowest K(m) (6.6 microm) for the cofactor. Despite the ability of all three enzymes to reduce aquacob(III)alamin, only MSR (the full-length form or the isolated FMN domain) enhanced the uptake of cobalamin by apo-MS. MSR was also the only diflavin reductase to reactivate the inert cob(II)alamin form of purified human MS (K(act) of 107 nm) isolated from Pichia pastoris. Our work shows that reactivation of cob(II)alamin MS and incorporation of cobalamin into apo-MS is enhanced through specific protein-protein interactions between the MSR FMN domain and MS.
The mystery of how the cyanide group in vitamin B12 or cyanocobalamin, discovered 60 years ago, is removed, has been solved by the demonstration that the trafficking chaperone, MMACHC, catalyzes a reductive decyanation reaction. Electrons transferred from NADPH via cytosolic flavoprotein oxidoreductases are used to cleave the cobalt–carbon bond with reductive elimination of the cyanide ligand. The product, cob(II)alamin, is a known substrate for assimilation into the active cofactor forms, methylcobalamin and 5′-deoxyadenosylcobalamin, and is bound in the “base-off” state that is needed by the two B12-dependent target enzymes, methionine synthase and methylmalonyl-CoA mutase. Defects in MMACHC represent the most common cause of inborn errors of B12 metabolism, and our results explain the observation that fibroblasts from these patients are poorly responsive to vitamin B12 but show some metabolic correction with aquocobalamin, a cofactor form lacking the cyanide ligand, which is mirrored by patients showing poorer clinical responsiveness to cyano- versus aquocobalamin.
• cobalamin
• flavin oxidoreductase
• methylmalonic aciduria
• homocystinuria
• cyanide
The aim of the present study was to examine the effects of cobalamin (Cbl) on the activity and expression of L-methylmalonyl-CoA mutase (MCM) in rat liver and cultured COS-7 cells. The MCM holoenzyme activity was less than 5% of the total (holoenzyme+apoenzyme) activity in the liver although rats were fed a diet containing sufficient Cbl. When weanling rats were maintained on a Cbl-deficient diet, the holo-MCM activity became almost undetectable at the age of 10 weeks. In contrast, a marked increase in the total-MCM activity occurred under the Cbl-deficient conditions, and at the age of 20 weeks it was about 3-fold higher in the deficient rats than in the controls (108 (SD 14.5) v. 35 (SD 8.5) nmol/mg protein per min (n 5); P<0.05). Western blot analysis confirmed that the MCM protein level increased significantly in the Cbl-deficient rats. However, the MCM mRNA level, determined by real-time PCR, was rather decreased. When COS-7 cells were cultured in a medium in which 10% fetal bovine serum was the sole source of Cbl, holo-MCM activity was barely detected. The supplementation of Cbl resulted in a large increase in the holo-MCM activity in the cells, but the activity did not exceed 30% of the total-MCM activity even in the presence of Cbl at 10 micromol/l. In contrast, the total-MCM activity was significantly decreased by the Cbl supplementation, indicating that Cbl deficiency results in an increase in the MCM protein level in COS-7 cells as well as in rat liver.
The granulocyte R-type cobalamin binding protein delivers cobalamin (Cbl) exclusively to hepatocytes, and transcobalamin II delivers Cbl to various mammalian cells. Both protein-Cbl complexes enter cells by pinocytosis, and the protein moieties are rapidly degraded in lysosomes. The liberated Cbl is subsequently bound to a high-molecular-weight intracellular cobalamin binding protein (ICB). The nature of ICB-Cbl is unknown but appears important because ICB-[57Co]Cbl is missing from cultured fibroblasts of a group of patients whose cells take up CN-[57Co]Cbl normally but do not convert it to either of its coenzyme forms. We have examined supernatants of sonicated rabbit livers and have found that 65% of the total endogenous Cbl elutes from Sephadex G-150 as ICB-Cbl and that this fraction also contains the two mammalian Cbl-dependent enzymes, methylmalonyl-CoA mutase (methylmalonyl-CoA CoA-carbonylmutase;EC 5.4.99.2) and methionine synthetase (tetrahydropteroylglutamate methyltransferase; 5-methyltetrahydropteroyl-L-glutamate:L-homocysteine-S-methyltransferase; EC 2.1.1.13). Gradient elution from DEAE-Sephadex reveals that 90--95% of the ICB--Cbl elutes with methylmalonyl-CoA mutase and 5--10% elutes with methionine synthetase. ICB--[57Co]Cbl first appears 2 hr after the intravenous injection of CN[57Co]Cbl bound to granulocyte R-type protein. This ICB-[57Co]Cbl is associated with either methylmalonyl-CoA mutase or methionine synthetase although the latter appears to be formed at a relatively faster rate. Our studies indicate that mammalian cells contain two ICBs, that these proteins are methylmalonyl-CoA mutase and methionine synthetase, and that the primary abnormality in the group of patients mentioned above lies at a step that is common to the formation of both Cbl coenzymes and that precedes the stable binding of Cbl to both methylmalonyl-CoA mutase and methionine synthetase.
Exposure of rats to nitrous oxide rapidly inactivated the cytosol enzyme, methionine synthetase, but the mitochondrial enzyme, methylmalonyl CoA mutase, seemed to be unaffected, although both enzymes require vitamin B12.
The synthesis of liver pteroylglutamates (folates) from injected [3-H]-pteroylglutamic acid was investigated in vitamin B-12 methionine-deficient rats and pair-fed controls using improved extraction and chromatographic procedures to identify the monoglutamyl derivatives present. Livers from deficient animals had significantly increased levels of radioactive 5-methyltetrahydropteroylglutamate detected after conjugase treatment of extracts and significantly decreased levels of radioactive tetrahydropteroylglutamate and formylated derivatives. However, that this is only a temporary effect and the result of a decreased rate of equilibration of the exogenous radioactivity was shown by measuring the fully equilibrated endogenous pools. This was done by microbiological assay of the endogenous liver folates with Lactobacillus casei. No significant difference was found between deficient animals and controls in the proportion of the endogenous microbiologically active derivatives present. These results in the rat do not support the idea that in vitamin B-12 deficiency the cellular folates accumulate as the reduced 5-methyl derivative, resulting in inadequate amount of the other cofactors to partipicate in nucleic acid biosynthesis.
We have produced severe vitamin B12 deficiency in rhesus monkeys by feeding them a defined experimental diet under controlled conditions. Five years after institution of the deficient diet, the morphology and counts of peripheral blood and bone marrow are normal. Gross visual impairment appeared in five of the monkeys between 33 and 45 months after the institution of the vitamin B12 deficient diet. Subsequently, in three of the visually impaired animals, a gradually progressive spastic paralysis of their hind limbs developed. Autopsies of six deficient animals showed degeneration of the peripheral visual pathway in all and of white matter in the spinal cord in four. Degeneration of several cranial nerve roots was found in four monkeys and a mild diffuse degeneration of cerebral white matter in four. The lesions in all affected parts of the central nervous system were bilaterally symmetrical and were indistinguishable from those due to B12 deficiency in the human. No abnormalities were found in one B12 supplemented control animal.
Male LEW/f Mai rats were exposed to an atmosphere of 20 per cent N2O, 20 per cent O2, and 60 per cent N2 for a maximum of 35 days. Evidence of injury to the seminiferous tubules was found in some animals by the second day. By 14 days, such damage was found in all animals. The toxic effect was confined to the spermatogenic cells, with consequent reduction in mature spermatozoa and appearance of multinucleated forms. Other cells within the testes were resistant to damage. Recovery of spermatogenesis occurred after return to room air for more than three days. Serum testosterone levels were not significantly affected during the prolonged exposure.
The state of vitamin B12-deficiency in rats was evaluated by determination of hepatic vitamin B12-dependent enzyme activities after the animals had fed on a vitamin B12-deficient soybean protein diet for 150 days. The effect of vitamin B12-deficiency on testicular tissue was also studied by morphological observations. Growth of vitamin B12-deficient rats was retarded and marked increase in urinary methylmalonic acid was observed. Vitamin B12 contents in the organs were depressed distinctly by the deficiency, especially in testes, vitamin B12 content decreased to 2.5 ng/g. Hepatic methionine synthase and methylmalonyl-CoA mutase activities showed striking depression to 5% of the control rats and extreme vitamin B12-deficiency was confirmed. Testes weight also showed marked decrease together with their relative weight per 100 g body weight. Morphological observations of testes of vitamin B12-deficient rats revealed atrophy of the seminiferous tubules and aplasia of sperms and spermatids. The above results proved that vitamin B12-deficiency affected rat testes, and suggested that the rat could be the animal model for elucidation of the mechanism of B12 action on testicular functions.
Cobalamin neuropathy was produced in Cape fruit bats (Rousettus aegyptiacus) by a cobalamin-free diet combined with intermittent exposure to nitrous oxide, which inactivates cobalamin. Cobalamin-deficient bats had low hepatic methylmalonyl-CoA mutase holoenzyme activity, with elevated plasma and urinary methylmalonic acid levels. No significant changes could be demonstrated in the concentration of odd- or branched-chain fatty acids in the nervous system. Supplementation of the cobalamin-free diet with methionine, valine or isoleucine delayed the onset of neuropathy, despite persistence of methylmalonic acid accumulation. Supplementation with any of the three amino acids was associated with elevation of hepatic methionine concentration. The action of valine and isoleucine in delaying the onset of neuropathy can be explained by their methionine-sparing effect. These results emphasize the central role of methionine in the cobalamin neuropathy and do not support the hypothesis that the neuropathy is related to an effect of cobalamin deficiency on the propionic acid pathway.
A new cobalt-containing nitrile hydratase was purified from extracts of urea-induced cells from Rhodococcus rhodochrous J1 in seven steps. At the last step, the enzyme was crystallized by adding ammonium sulfate. Nitrile hydratase was a 500-530-kDa protein composed of two different subunits (alpha subunit 26 kDa, beta subunit 29 kDa). The enzyme contained approximately 11-12 mol cobalt/mol enzyme. A concentrated solution of highly purified nitrile hydratase exhibited a broad absorption spectrum in the visible range, with an absorption maxima at 410 nm. The enzyme had a wide substrate specificity. Aliphatic saturated or unsaturated nitriles as well as aromatic nitriles, were substrates for the enzyme. The optimum pH of the hydratase was pH 6.5-6.8. The enzyme was more stable than ferric nitrile hydratases. The amino-terminal sequence of each subunit of R. rhodochrous J1 enzyme was determined and compared with that of ferric nitrile hydratases. Prominent similarities were observed with the beta subunit. However, the amino acid sequence of the alpha subunit from R. rhodochrous J1 was quite different from that of the ferric enzymes.
The binding of several corrinoids to the binding site of human intrinsic factor, transcobalamin or haptocorrin was investigated, p-Cresolyl cobamide and 2-amino-vitamin B12 are complete corrinoids, whose nucleotide at the lower face of the corrin ring is not coordinated to the cobalt. These corrinoids were greater than or equal to 10(3) times less efficiently recognized by intrinsic factor or transcobalamin than vitamin B12, which contains a Co-coordinated nucleotide. Pseudovitamin B12, with a weak Co-N coordination bond, revealed only moderate affinity to intrinsic factor. From these findings it is concluded that the cobamide binding to intrinsic factor and transcobalamin is strongly affected by the Co-N coordination bonds of their lower cobalt nucleotide ligands. We suggest that the Co-N coordination bond positions the nucleotide at a critical distance to the corrin ring, which is recognized by the binding proteins. Human haptocorrin, however, disclosed to distinctive selectivity regarding the different corrinoid structures. The protein bound all corrinoids with similar efficiency, independent of the strength of their Co-N coordinations, or the structures of their lower Co alpha ligands. Hence, the corrin ring, rather than a structural feature induced by the Co-N coordination, has to be considered responsible for the corrinoid binding to haptocorrin.
Erythropoietin (Epo), the hormone that stimulates red blood cell production, is synthesized in the kidney and liver in response
to hypoxia. The human hepatoma cell line Hep3B regulates its production of Epo in a physiologic manner. Either hypoxia or
cobalt chloride markedly increases expression of Epo mRNA as well as production of biologically active and immunologically
distinct Epo protein. New protein synthesis is required before the induction of increased levels of hypoxia- or cobalt-induced
Epo mRNA. Hypoxia, cobalt chloride, and nickel chloride appear to stimulate Epo production through a common pathway. The inhibition
of Epo production at low partial pressures of oxygen by carbon monoxide provides evidence that a heme protein is integrally
involved in the oxygen-sensing mechanism. This hypothesis is further supported by the finding that when heme synthesis is
blocked, hypoxia-, cobalt-, and nickel-induced Epo production are all markedly inhibited. A model is proposed in which a ligand-dependent
conformational change in a heme protein accounts for the mechanism by which hypoxia as well as cobalt and nickel stimulate
the production of Epo.
Pigs were treated with N2O which is known to impair vitamin B12 function in vivo. Such pigs demonstrated an inability to gain weight, progressive ataxia, and spinal neuropathy. The ataxia was totally and the neuropathy partially preventable by dietary methionine supplementation. Methionine synthase activity was inhibited in both the liver and brain. There was a marked elevation of S-adenosylhomocysteine in the neural tissues and a concomitant failure of S-adenosylmethionine to rise and thus maintain the methylation ratio, except when supplementary dietary methionine was added. In contrast, the methylation ratio in the rat was affected to a lesser extent. The neuropathy, it is suggested, is caused by raised S-adenosylhomocysteine levels in neural tissue; as a result, the methylation ratio is inverted and S-adenosylmethionine-dependent methylation reactions are inhibited.
Two components of extract separable by DEAF-cellulose chromatography have been found to function together to convert the apoenzyme form of the N5-methyltetrahydrofolate-homocysteine transmethylase and adenosyl B12 to holoenzyme in the presence of DPNH and homocysteine. They also form holoenzyme from hydroxo-B12 and cyano-B12 and constitute a DPNH-dependent reducing system that promotes the formation of methionine by holoenzyme.