Investigation of Streptomyces antibioticus tyrosinase reactivity toward chlorophenols
Tyrosinase (Ty) is a copper-containing enzyme ubiquitously distributed in nature. In recent years, Ty has attracted interest as a potential detoxifying agent for xenobiotic compounds with phenolic structure. Among these, chlorophenols are particularly relevant pollutants, commonly found in waste waters. The activity of Streptomyces antibioticus tyrosinase toward isomeric monochlorophenols was studied. Tyrosinase oxidizes both 3- and 4-chlorophenol to the same product, 4-chloro-1,2-ortho-quinone, which subsequently undergoes a nucleophilic substitution reaction at the chlorine atom by excess phenol to give the corresponding phenol-quinone adduct. By contrast, 2-chlorophenol is not reactive and acts as a competitive inhibitor. Docking calculations suggest that the substrates point to one of the copper atoms of the dinuclear center (copper B) and appear to interact preferentially with one of the two coordinated oxygen atoms. The approach of the substrate toward the active site is favored by a π-stacking interaction with one of the copper-coordinated histidines (His194) and by a hydrogen bonding interaction with the O1 oxygen. With this study, we provide the first characterization of the early intermediates in the biotechnologically relevant reaction of Ty with chlorophenols. Additionally, combining experimental evidences with molecular modeling simulations, we propose a detailed reaction scheme for Ty-mediated oxidation of monochlorophenols.
Available from: Rashid Nazir
- "Bacterial melanin has been shown to interact with double-stranded DNA and its cellular localization may inhibit cell metabolism (Geng et al. 2010). Bacterial tyrosinases may also act on particular phenolic compounds, such as chlorophenols (Marino et al. 2011) and fluorophenols (Battaini et al. 2002). The role of the unique tyrosinase found in the B. terrae BS001 genome is not well understood, but it may serve the organism to cope with stressful environments and detoxify fungal/plant phenolic compounds. "
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ABSTRACT: Burkholderia terrae strain BS001, obtained as an inhabitant of the mycosphere of Laccaria proxima (a close relative of Lyophyllum sp. strain Karsten), actively interacts with Lyophyllum sp. strain Karsten. We here summarize the remarkable ecological behavior of B. terrae BS001 in the mycosphere and add key data to this. Moreover, we extensively analyze the approximately 11.5-Mb five-replicon
genome of B. terrae BS001 and highlight its remarkable features. Seventy-nine regions of genomic plasticity (RGP), that is, 16.48% of the total
genome size, were found. One 70.42-kb RGP, RGP76, revealed a typical conjugal element structure, including a full type 4 secretion
system. Comparative analyses across 24 related Burkholderia genomes revealed that 95.66% of the total BS001 genome belongs to the variable part, whereas the remaining 4.34% constitutes
the core genome. Genes for biofilm formation and several secretion systems, under which a type 3 secretion system (T3SS),
were found, which is consistent with the hypothesis that T3SSs play a role in the interaction with Lyophyllum sp. strain Karsten. The high number of predicted metabolic pathways and membrane transporters suggested that strain BS001
can take up and utilize a range of sugars, amino acids and organic acids. In particular, a unique glycerol uptake system was
found. The BS001 genome further contains genetic systems for the degradation of complex organic compounds. Moreover, gene
clusters encoding nonribosomal peptide synthetases (NRPS) and hybrid polyketide synthases/NRPS were found, highlighting the
potential role of secondary metabolites in the ecology of strain BS001. The patchwork of genetic features observed in the
genome is consistent with the notion that 1) horizontal gene transfer is a main driver of B. terrae BS001 adaptation and 2) the organism is very flexible in its ecological behavior in soil.
Genome Biology and Evolution 06/2014; 6(7). DOI:10.1093/gbe/evu126 · 4.23 Impact Factor
Available from: Kamal Uddin Zaidi
- "The application of a polyphenol oxidase enzyme such as tyrosinase in removal of phenol and its derivatives has become very important and effective method . The tyrosinase from S. antibioticus, for example, had activity on industrial pollutants such as 3- and 4-chlorophenols and 3- and 4-fluorophenols . The application of bacterial tyrosinase to the treatment of contaminated wastewaters has recently been reviewed and can be done either with tyrosinase producing stains or with the enzyme in an immobilized form as protagonist [102, 103]. "
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ABSTRACT: Tyrosinase is a natural enzyme and is often purified to only a low degree and it is involved in a variety of functions which mainly catalyse the o-hydroxylation of monophenols into their corresponding o-diphenols and the oxidation of o-diphenols to o-quinones using molecular oxygen, which then polymerizes to form brown or black pigments. The synthesis of o-diphenols is a potentially valuable catalytic ability and thus tyrosinase has attracted a lot of attention with respect to industrial applications. In environmental technology it is used for the detoxification of phenol-containing wastewaters and contaminated soils, as biosensors for phenol monitoring, and for the production of L-DOPA in pharmaceutical industries, and is also used in cosmetic and food industries as important catalytic enzyme. Melanin pigment synthesized by tyrosinase has found applications for protection against radiation cation exchangers, drug carriers, antioxidants, antiviral agents, or immunogen. The recombinant V. spinosum tryosinase protein can be used to produce tailor-made melanin and other polyphenolic materials using various phenols and catechols as starting materials. This review compiles the recent data on biochemical and molecular properties of microbial tyrosinases, underlining their importance in the industrial use of these enzymes. After that, their most promising applications in pharmaceutical, food processing, and environmental fields are presented.
Biochemistry Research International 05/2014; 2014(2):854687. DOI:10.1155/2014/854687
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ABSTRACT: The electrochemistry of some quinones has been focused to determine the mode of interaction in presence of polyalcohols. Three compounds of each family (benzoquinones, naphthoquinones and anthraquinones) were investigated through cyclic voltammetry in the presence of ethylene glycol (a diol)) and glycerol (a triol) in dichloromethane and acetonitrile at 25°C. The observed positive shift in both the waves of the quinone with successive addition of alcohol was attributed to hydrogen bonding in the quinone-alcohol couple. “Two electron one step” electron transfer mechanism was proposed for the increase in the first wave height at the expense of second. The depletion of the first anodic wave at higher concentration of polyalcohol was rationalized in terms of protonation-deprotonation mechanism. A prior peak observed in the presence of glycerol was ascribed to the hydrogen bonding of the alcohol with neutral quinone. The difference in basicity strength within a family as well as among the three quinone families was also addressed in view of the interaction effectiveness.
Russian Journal of Electrochemistry 04/2013; 49(4). DOI:10.1134/S1023193513040034 · 0.76 Impact Factor
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