Arthur J L Cooper

• PhD, DSc
• Professor Emeritus at New York Medical College

Simple Summary Many types of cancer cells utilize the common amino acid l-glutamine to maintain their metabolic demands for energy and the nitrogen required for DNA synthesis. Versatility to control energy metabolism from l-glutamine (anaplerosis) is promoted by the use of two distinct pathways. The first (pathway 1; the canonical pathway) is as fo...

Many cancers utilize L-glutamine as a major energy source. This “L-glutamine addiction” involves a well-characterized pathway whereby L-glutamine is hydrolyzed by a glutaminase (GLS) to L-glutamate, which is then converted to α-ketoglutarate, the carbons of which enter the tricarboxylic acid (TCA) cycle. However, mammalian tissues/cancers possess a...

In the glutaminase II pathway (which we now refer to as the glutamine transaminase-ω-amidase (GTωA) pathway), l-glutamine is transaminated to α-ketoglutaramate (KGM), which, in turn, is hydrolyzed to α-ketoglutarate and ammonia by an enzyme known as ω-amidase. Despite the fact that the GTωA pathway was discovered more than 70 years ago, and is wide...

Dietary methionine restriction (MR) increases longevity by improving health. In experimental models, MR is accompanied by decreased cystathionine β-synthase activity and increased cystathionine γ-lyase activity. These enzymes are parts of the transsulfuration pathway which produces cysteine and 2-oxobutanoate. Thus, the decrease in cystathionine β-...

Metabolic Recycling In article number 2200233, Anne Le and co‐workers study cancer relapse after treatment and the phenomenon of metabolic recycling, which may help to partially explain why cancer relapse occurs. Specifically, they find that surviving live cancer cells are able to take up the metabolites from the post‐therapy environment containing...

Relapses negatively impact cancer patient survival due to the tumorigenesis ability of surviving cancer cells post‐therapy. Efforts are needed to better understand and combat this problem. This study hypothesized that dead cell debris post‐radiation therapy creates an advantageous microenvironment rich in metabolic materials promoting the growth of...

Reactive oxygen species (ROS) are important mediators of both physiological and pathophysiological signal transduction in the cardiovascular system. The effects of ROS on cellular processes depend on the concentration, localization, and duration of exposure. Cellular stress response mechanisms have evolved to mitigate the negative effects of acute...

Nit2/ω-amidase catalyzes the hydrolysis of α-ketoglutaramate (KGM, the α-keto acid analogue of glutamine) to α-ketoglutarate and ammonia. The enzyme also catalyzes the amide hydrolysis of monoamides of 4- and 5-C-dicarboxylates, including α-ketosuccinamate (KSM, the α-keto acid analogue of asparagine) and succinamate (SM). Here we describe an inexp...

The use of metabolomics technologies and stable isotope labeling recently enabled us to discover an unexpected role of N-acetyl-aspartyl-glutamate (NAAG): NAAG is a glutamate reservoir for cancer cells. In the current study, we first found that glucose carbon contributes to the formation of NAAG and its precursors via glycolysis, demonstrating the...

s Aromatic amino acids (AAAs) are parts of the building blocks for protein synthesis. They are also precursors in the synthesis of many other important compounds that play some key roles in the biochemistry and physiology of living organisms. All living species have evolved AAA metabolic pathways to best fit their physiological needs and to adapt t...

The asparaginase II pathway consists of an asparagine transaminase [L-asparagine + α-keto acid ⇆ α-ketosuccinamate + L-amino acid] coupled to ω-amidase [α-ketosuccinamate + H2O → oxaloacetate + NH4⁺]. The net reaction is: L-asparagine + α-keto acid + H2O → oxaloacetate + L-amino acid + NH4⁺. Thus, in the presence of a suitable α-keto acid substrate...

In rapidly dividing cells, including many cancer cells, l-glutamine is a major energy source. Utilization of glutamine is usually depicted as: l-glutamine → l-glutamate (catalyzed by glutaminase isozymes; GLS1 and GLS2), followed by l-glutamate → α-ketoglutarate [catalyzed by glutamate-linked aminotransferases or by glutamate dehydrogenase (GDH)]....

Small biomolecules, such as coenzyme A (CoA) and acetyl coenzyme A (acetyl-CoA), play vital roles in the regulation of cellular energy metabolism. In this paper, we evaluated the delayed effect of the potent hepatotoxin thioacetamide (TAA) on the concentrations of CoA and acetyl-CoA in plasma and in different rat tissues. Administration of TAA nega...

A novel cosegregating splice site variant in the Dynactin-1 (DCTN1) gene was discovered by Next Generation Sequencing (NGS) in a family with a history of bipolar disorder (BD) and major depressive diagnosis (MDD). Psychiatric illness in this family follows an autosomal dominant pattern. DCTN1 codes for the largest dynactin subunit, namely p150Glued...

α-Aminoadipic semialdehyde and its cyclic form (Δ¹-piperideine-6-carboxylate) accumulate in patients with α-aminoadipic semialdehyde dehydrogenase (AASADH; antiquitin; ALDH7A1) deficiency. Δ¹-Piperideine-6-carboxylate reacts with pyridoxal 5'-phosphate (PLP) to form a Knoevenagel condensation product, resulting in pyridoxine-dependent epilepsy. Des...

Many tumors readily convert l-glutamine to α-ketoglutarate. This conversion is almost invariably described as involving deamidation of l-glutamine to l-glutamate followed by a transaminase (or dehydrogenase) reaction. However, mammalian tissues possess another pathway for conversion of l-glutamine to α-ketoglutarate, namely the glutaminase II pathw...

DOI: 10.1002/pmic.201800451 Much like the classic arcade game “Whack‐a‐Mole”, cancer cells are able to upregulate a different metabolic pathway when one pathway is inhibited. Specifically, using metabolomics technologies with isotopic labelling, Sunag Udupa et al. demonstrate in article number 1800451 the production of glutamate from glutamine via...

The targeting of glutamine metabolism specifically via pharmacological inhibition of glutaminase 1 (GLS1) has been translated into clinical trials as a novel therapy for several cancers. The results, though encouraging, show room for improvement in terms of tumor reduction. In this study, the glutaminase II pathway is found to be upregulated for gl...

Cystamine is commonly used as a transglutaminase inhibitor. This disulfide undergoes reduction in vivo to the aminothiol compound, cysteamine. Thus, the mechanism by which cystamine inhibits transglutaminase activity in vivo could be due to either cystamine or cysteamine, which depends on the local redox environment. Cystamine inactivates transglut...

A novel co-segregating splice site variant in the Dynactin-1 (DCTN1) gene was discovered by Next Generation Sequencing (NGS) in a family with a history of bipolar disorder (BD) and major depressive diagnosis (MDD). Psychiatric illness in this family follows an autosomal dominant pattern. DCTN1 codes for the largest dynactin subunit, namely p150 Glu...

Cellular thiols such as cysteine spontaneously and readily react with the respiratory intermediate fumarate, resulting in the formation of stableS-(2-succino)-adducts. Fumarate-mediated succination of thiols increases in certain tumors and in response to glucotoxicity associated with diabetes. Therefore,S-(2-succino)-adducts such asS-(2-succino)cys...

Coenzyme A (CoA) and acetyl-coenzyme A (acetyl-CoA) play essential roles in cell energy metabolism. Dysregulation of the biosynthesis and functioning of both compounds may contribute to various pathological conditions. We describe here a simple and sensitive HPLC-UV based method for simultaneous determination of CoA and acetyl-CoA in a variety of b...

Ammonia is neurotoxic, and chronic hyperammonemia is thought to be a major contributing factor to hepatic encephalopathy in patients with liver disease. Portacaval shunting of rats is used as an animal model to study the detrimental metabolic effects of elevated ammonia levels on body tissues, particularly brain and testes that are deleteriously ta...

Significance The genomes of the vast majority of eukaryotes encode a protein [named nitrilase-like protein 1 (Nit1) in humans and mice] whose enzymatic function has long been unknown. We show here that the mammalian Nit1 and the corresponding yeast protein efficiently hydrolyze the deaminated form of the common intracellular antioxidant glutathione...

Many enzymes make “mistakes”. Consequently, repair enzymes have evolved to correct these mistakes. For example, lactate dehydrogenase (LDH) and mitochondrial malate dehydrogenase (mMDH) slowly catalyze the reduction of 2-oxoglutarate (2-OG) to the oncometabolite l-2-hydroxyglutarate (l-2-HG). l-2-HG dehydrogenase corrects this error by converting l...

Thyroid hormones have long been known to play an essential role in brain growth and development, with cytoplasmic thyroid hormone binding proteins (THBPs) playing a critical role in thyroid hormone bioavailability. A major mammalian THBP is μ-crystallin (CRYM), which was originally characterized by its ability to strongly bind thyroid hormones in a...

Hepatic encephalopathy (HE) is a major complication of liver failure/disease which frequently develops during the progression of end-stage liver disease. This metabolic neuropsychiatric syndrome involves a spectrum of symptoms, including cognition impairment, attention deficits and motor dysfunction which eventually can progress to coma and death....

Two 4-fluoro-l-glutamine diastereoisomers [(2S,4R)-4-FGln, (2S,4S)-4-FGln] were previously developed for positron emission tomography. Label uptake into two tumor cell types was greater with [¹⁸F](2S,4R)-4-FGln than with [¹⁸F](2S,4S)-4-FGln. In the present work we investigated the enzymology of two diastereoisomers of 4-FGln, two diastereoisomers o...

Many common metabolites are intrinsically unstable and reactive, and hence prone to chemical (i.e. non-enzymatic) damage in vivo. Although this fact is widely recognized, the purely chemical side-reactions of metabolic intermediates can be surprisingly hard to track down in the literature and are often treated in an unprioritized case-by-case way....

Endostatin (EST), an antiangiogenic factor, is enriched in aging kidneys. EST is also an interactive partner of transglutaminase 2 (TG2), an enzyme that cross-links extracellular matrix proteins. Here we tested whether EST and TG2 play a role in the fibrosis of aging. In wild-type mice, aging kidneys exhibited a 2- to 4-fold increase in TG2 paralle...

Glutamate is present in the brain at an average concentration—typically 10–12 mM—far in excess of those of other amino acids. In glutamate-containing vesicles in the brain, the concentration of glutamate may even exceed 100 mM. Yet because glutamate is a major excitatory neurotransmitter, the concentration of this amino acid in the cerebral extrace...

Here we describe a simple high performance liquid chromatography procedure for the simultaneous detection and quantitation in standard solutions of thirteen important metabolites of cellular energy metabolism, including nine tricarboxylic acid cycle components and four additional metabolites. The metabolites are detected by their absorbance at 210...

Many potentially toxic electrophilic xenobiotics and some endogenous compounds are detoxified by conversion to the corresponding glutathione S-conjugate, which is metabolized to the N-acetylcysteine S-conjugate (mercapturate) and excreted. Some mercapturate pathway components, however, are toxic. Bioactivation may occur when the glutathione S-conju...

Glutamine metabolism is largely controlled by two enzyme pathways: 1) Conversion of glutamine to glutamate catalyzed by glutaminases, followed by conversion of glutamate to α-ketoglutarate by a glutamate-linked aminotransferases (or by the action of glutamate dehydrogenase); and 2) conversion of glutamine to α-ketoglutaramate (KGM) catalyzed by glu...

In mammals, two major routes exist for the metabolic conversion of L-glutamine to α-ketoglutarate. The most widely studied pathway involves the hydrolysis of L-glutamine to L-glutamate catalyzed by glutaminases, followed by the conversion of L-glutamate to α-ketoglutarate by the action of an L-glutamate-linked aminotransferase or via the glutamate...

The following article addresses some seemingly paradoxical observations concerning cerebral glutamine synthetase in ischemia-reperfusion injury. In the brain, this enzyme is predominantly found in astrocytes and catalyzes part of the glutamine-glutamate cycle. Glutamine synthetase is also thought to be especially sensitive to inactivation by the ox...

Recently, crystalized mouse ketimine reductase/CRYM complexed with NADPH was found to have pyruvate bound in its active site. We demonstrate that the enzyme binds α-keto acids, such as pyruvate, in solution, and catalyzes the formation of N-alkyl-amino acids from alkylamines and α-keto acids (via reduction of imine intermediates), but at concentrat...

It is now recognized that enzymatic or chemical side-reactions can convert normal metabolites to useless or toxic ones and that a suite of enzymes exists to mitigate such metabolite damage. Examples are the reactive imine/enamine intermediates produced by threonine dehydratase, which damage the pyridoxal 5'-phosphate cofactor of various enzymes cau...

Mammalian ketimine reductase is identical to μ-crystallin (CRYM)-a protein that is also an important thyroid hormone binding protein. This dual functionality implies a role for thyroid hormones in ketimine reductase regulation and also a reciprocal role for enzyme catalysis in thyroid hormone bioavailability. In this research we demonstrate potent...

Three of the four kynurenine aminotransferases (KAT I, II, and IV) that synthesize kynurenic acid, a neuromodulator, are identical to glutamine transaminase K (GTK), α-aminoadipate aminotransferase, and mitochondrial aspartate aminotransferase, respectively. GTK/KAT I and aspartate aminotransferase/KAT IV possess cysteine S-conjugate β-lyase activi...

The understanding of sulfur bonding is undergoing change. Old theories on hypervalency of sulfur and the nature of the chalcogen-chalcogen bond are now questioned. At the same time, there is a rapidly expanding literature on the effects of sulfur in regulating biological systems. The two fields are inter-related because the new understanding of the...

RidA (for Reactive Intermediate Deaminase A) proteins are ubiquitous, yet their function in eukaryotes is unclear. It is known that deleting Salmonella enterica ridA causes Ser sensitivity and that S. enterica RidA and its homologs from other organisms hydrolyze the enamine/imine intermediates that Thr dehydratase forms from Ser or Thr. In S. enter...

Glutathionylation is generally a reversible posttranslational modification that occurs to cysteine residues that have been exposed to reactive oxygen species (P-SSG). This cyclical process can regulate various clusters of proteins, including those involved in critical cellular signaling functions. However, certain conditions can favor the formation...

Parkinson's disease is characterized by the progressive and selective loss of dopaminergic neurons in the substantia nigra. It has been postulated that endogenously formed 5-S-cysteinyldopamine (CysDA) and its metabolites may be, in part, responsible for this selective neuronal loss, although the mechanisms by which they contribute to such neurotox...

We read with great interest the article by Wang et al,1 who reported that the synthesis of the gasotransmitter H2S is impaired in preeclampsia and concluded that H2S may contribute to the pathogenesis of preeclampsia. H2S is only 1 of several contributors to the highly redox-sensitive labile sulfur pool comprising free H2S, acid-labile sulfide, and...

Flavin-dependent monooxygenases and oxidoreductases are located at critical branch points in the biosynthesis and metabolism of cholesterol and vitamin D. These flavoproteins function as obligatory intermediates that accept 2 electrons from NAD(P)H with subsequent 1-electron transfers to a variety of cytochrome P450 (CYP) heme proteins within the m...

In a contribution to this Research Topic Erkki Somersalo and Daniela Calvetti carried out a mathematical analysis of neurotransmitter pathways in brain, modeling compartmental nitrogen flux among several major participants – ammonia, glutamine, glutamate, GABA, and selected amino acids. This analysis is important because cerebral nitrogen metabolis...

Glutamine metabolism is generally regarded as proceeding via glutaminase-catalyzed hydrolysis to glutamate and ammonia, followed by conversion of glutamate to α-ketoglutarate catalyzed by glutamate dehydrogenase or by a glutamate-linked aminotransferase (transaminase). However, another pathway exists for the conversion of glutamine to α-ketoglutara...

At high concentrations, the glutamine synthetase inhibitor L-methionine-S,R-sulfoximine (MSO) is a convulsant, especially in dogs. Nevertheless, sub-convulsive doses of MSO are neuroprotective in rodent models of hyperammonemia, acute liver disease, and amyotrophic lateral sclerosis and suggest MSO may be clinically useful. Previous work has also s...

Epidemiological findings show that chalcogen-containing amino acids reduce cancer risks. Aminotransferases catalyze β-elimination reactions and transamination reactions with a) several cysteine S-conjugates [RSCH 2 CH(NH 3 +)CO-] including S-allyl-L-cysteine (SAC, R = CH 2 =CHCH 2-), S-allylmercapto-L-cysteine (SAMC, R = CH 2 =CHCH 2 Sand and b) se...

The lysine catabolism pathway differs in adult mammalian brain from that in extracerebral tissues. The saccharopine pathway is the predominant lysine degradative pathway in extracerebral tissues, whereas the pipecolate pathway predominates in adult brain. The two pathways converge at the level of ∆(1)-piperideine-6-carboxylate (P6C), which is in eq...

The Nit (nitrilase-like) protein subfamily constitutes branch 10 of the nitrilase superfamily. Nit proteins are widely distributed in nature. Mammals possess two members of the Nit subfamily, namely Nit1 and Nit2. Based on sequence similarity, yeast Nit2 (yNit2) is a homologue of mouse Nit1, a tumour-suppressor protein whose substrate specificity i...

Please note this is a Correspondence submission.

Chemoprevention trials show that Se-methyl-L-selenocysteine (MSC) and L-selenomethionine (SM) reduce tumor frequency of prostate, lung, liver and colon. Mechanisms underlying the protective effects of selenoamino acids remain unclear. Our studies show that GTK and GTL in the presence of α-keto acid co-substrates (ketomethiolbutyrate, phenylpyruvate...

Chemoprevention trials show that MSC and SM reduce the risk of prostate, lung, and colon cancers. Mechanisms underlying the protective effects of selenoamino acids remain unclear. Our studies show that GTK and GTL in the presence of α-keto acid co-substrates (α-keto-γ-methiolbutyrate, phenylpyruvate, glyoxylate) transaminate MSC and SM to selenoket...

A key intermediate in the glutamate dehydrogenase (GDH)-catalyzed reaction is an imine. Mechanistically, therefore, GDH exhibits similarities to the ketimine reductases. In the current review, we briefly discuss (a) the metabolic importance of the GDH reaction in liver and brain, (b) the mechanistic similarities between GDH and the ketimine reducta...

Two enzymatic assays were developed for the analysis of α-ketoglutaramate (KGM)-an important biomarker of hepatic encephalopathy and other hyperammonemic diseases. In both procedures, KGM is first converted to α-ketoglutarate (KTG) via a reaction catalyzed by ω-amidase (AMD). In the first procedure, KTG generated in the AMD reaction initiates a bio...

Glutamine synthetase (GS) is highly active in astrocytes, and these cells are physiologically and morphologically compromised by hyperammonemia. Hyperammonemia in end-stage acute liver failure (ALF) is often associated with cerebral edema and astrocyte pathology/swelling. Many studies of animal models of hyperammonemia, and, more recently, nuclear...

Background: Human Nit2/ω-amidase is a putative tumor suppressor. Results: Both the catalytic triad and loop 116–128 of hNit2 play an essential role in the enzyme-substrate binding and enzymatic activity. Conclusion: The results of MD simulations are consistent with the kinetic analysis obtained with substrates α-ketoglutaramate and succinamate. Sig...

In the brain, glutamine synthetase (GS), which is located predominantly in astrocytes, is largely responsible for the removal of both blood-derived and metabolically generated ammonia. Thus, studies with [(13)N]ammonia have shown that about 25 % of blood-derived ammonia is removed in a single pass through the rat brain and that this ammonia is inco...

Many cancer cells have a strong requirement for glutamine. As an aid for understanding this phenomenon the (18)F-labeled 2S,4R stereoisomer of 4-fluoroglutamine [(2S,4R)4-FGln] was previously developed for in vivo positron emission tomography (PET). In the present work, comparative enzymological studies of unlabeled (2S,4R)4-FGln and its deamidated...

Transglutaminases catalyze the formation of γ-glutamylamines utilizing glutamyl residues and amine-bearing compounds such as lysyl residues and polyamines. These γ-glutamylamines can be released from proteins by proteases in an intact form. The free γ-glutamylamines can be catabolized to 5-oxo-L-proline and the free amine by γ-glutamylamine cyclotr...

Anthropogenic practices and recycling in the environment through natural processes result in release of potentially harmful levels of mercury into the biosphere. Mercury, especially organic forms, accumulates in the food chain. Mercury reacts readily with sulfur-containing compounds and often exists as a thiol S-conjugate, such as the l-cysteine (C...

Growth and energy demands of cancer cells rely on a constant supply of glutamine (Gln), a key nutrient that provides anaplerotic precursors for the biosynthesis of macromolecules. In most transformed cells, Gln contributes significantly to the keto acid pool that feeds anaplerosis. The amide moiety of Gln is hydrolyzed to yield ammonia via a reacti...

Introduction: Depending in part on the glutathione:glutathione disulfide ratio, reversible protein glutathionylation to a mixed disulfide may occur. Reversible glutathionylation is important in protecting proteins against oxidative stress, guiding correct protein folding, regulating protein activity and modulating proteins critical to redox signal...

Hyperammonemia is a major contributing factor to the encephalopathy associated with liver disease. It is now generally accepted that hyperammonemia leads to toxic levels of glutamine in astrocytes. However, the mechanism by which excessive glutamine is toxic to astrocytes is controversial. Nevertheless, there is strong evidence that glutamine-induc...

A synthetic polyanion composed of styrene, maleic anhydride, and methacrylic acid (molar ratio 56:37:7) significantly inhibited the respiration of isolated rat liver mitochondria in a time-dependent fashion that correlated with 1) collapse of the mitochondrial membrane potential and 2) high amplitude mitochondrial swelling. The process is apparentl...

Citrin is the hepatic mitochondrial aspartate-glutamate carrier that is encoded by the gene SLC25A13. Citrin deficiency often leads to hyperammonemia, for which the current treatment concept is different from that for primary hyperammonemias. Metabolite level diagnosis, often referred to as chemical diagnosis, is not always successful in identifyin...

Overview Paracatalytic Reactions: Definition Discovery of Enzyme-Catalyzed Oxygenase Side Reactions: Rubisco Reaction of Carbanions with Oxygen Catalyzed by Selected Enzymes (Excluding Pyridoxal 50′-Phosphate-Containing Enzymes) Oxidation Reactions Catalyzed by PLP-Containing Amino Acid Decarboxylases Mechanisms Contributing to the Oxidation Reacti...

α-Ketoglutaramate (KGM) is the α-keto acid analogue of glutamine, which exists mostly in equilibrium with a lactam form (2-hydroxy-5-oxoproline) under physiological conditions. KGM was identified in human urine and its concentration quantified by gas chromatography/mass spectrometry (GC/MS). The keto acid was shown to be markedly elevated in urine...

J. Neurochem. (2011) 118, 379–387. Ketimine reductase (E.C. 1.5.1.25) was purified to apparent homogeneity from lamb forebrain by means of a rapid multi-step chromatography protocol. The purified enzyme was identified by MS/MS (mass spectrometry) as μ-crystallin. The identity was confirmed by heterologously expressing human μ-crystallin in Escheric...

Many potentially toxic electrophiles react with glutathione to form glutathione S-conjugates in reactions catalyzed or enhanced by glutathione S-transferases. The glutathione S-conjugate is sequentially converted to the cysteinylglycine-, cysteine- and N-acetyl-cysteine S-conjugate (mercapturate). The mercapturate is generally more polar and water...

Many diseases, most with a strong neurodegenerative component, are now known to result from an expansion of a trinucleotide repeat sequence within the genome. In many cases, the longer the repeat the earlier the onset, and the more rapid and severe is the disease progression. Almost all of these diseases may be divided into three groups. In the fir...