Investigation of Streptomyces antibioticus tyrosinase reactivity toward chlorophenols
ABSTRACT 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.
SourceAvailable from: Sharique Ali[Show abstract] [Hide abstract]
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.05/2014; 2014:854687. DOI:10.1155/2014/854687
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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 ~11.5 Mb five-replicon genome of B. terrae BS001, and highlight its remarkable features. Seventy-nine regions of genomic plasticity (RGP), i.e. 16.48% of the total genome size, were found. One 70.422 kb RGP, RGP76, revealed a typical conjugal element structure, including a full type 4 secretion system (T4SS). Comparative analyses across 24 related Burkholderia genomes revealed 95.66% of the total BS001 genome to belong 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 contained genetic systems for the degradation of complex organic compounds. Moreover, gene clusters encoding nonribosomal peptide synthetases (NRPS) and hybrid polyketide synthases/nonribosomal peptide synthetases (PKS/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 · 4.53 Impact Factor
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ABSTRACT: Forty-five strains that produced diffusive pigment were isolated from 40 soil samples. Maximum pigment was produced by a Streptomyces kathirae strain designated SC-1. The diffused pigment was characterized by UV-Vis and infrared spectroscopy, mass spectrometry and (1) H-NMR, and was confirmed as melanin. Indeed, this might be the first report of melanin production by S. kathirae. To enhance the melanin production, The culture medium was optimized by conducting a series of batch fermentations in a defined medium, and statistically analyzed the results using a response surface method. The optimal culture medium (g/L) was determined as amylodextrine 3.3, yeast extract 37, NaCl 5, CaCl2 0.1, CuSO4 54.4 μmol/L. The pH of this medium was 6.0. Under the optimal conditions, the melanin concentration was maximized at 13.7 g/L, approximately 8.6-fold higher than obtained in suboptimal medium. To our knowledge, the results were novel records on melanin fermentation, and identify an excellent candidate for industrial-scale microbial fermentation of melanin. This article is protected by copyright. All rights reserved.FEMS Microbiology Letters 06/2014; 357(1). DOI:10.1111/1574-6968.12497 · 2.72 Impact Factor