Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.10.3.2 (laccase)
4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RL5, a gene coding for a novel polyphenol oxidase, was identified through activity screening of a metagenome expression library from bovine rumen microflora. Characterization of the recombinant protein produced in Escherichia coli revealed a multipotent capacity to oxidize a wide range of substrates (syringaldazine > 2,6-dimethoxyphenol > veratryl alcohol > guaiacol > tetramethylbenzidine > 4-methoxybenzyl alcohol > 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) >> phenol red) over an unusually broad range of pH from 3.5 to 9.0. Apparent Km and kcat values for ABTS, syringaldazine, and 2,6-dimetoxyphenol obtained from steady-state kinetic measurements performed at 40 degrees C, pH 4.5, yielded values of 26, 0.43, and 0.45 microm and 18, 660, and 1175 s(-1), respectively. The Km values for syringaldazine and 2,6-dimetoxyphenol are up to 5 times lower, and the kcat values up to 40 times higher, than values previously reported for this class of enzyme. RL5 is a 4-copper oxidase with oxidation potential values of 745, 400, and 500 mV versus normal hydrogen electrode for the T1, T2, and T3 copper sites. A three-dimensional model of RL5 and site-directed mutants were generated to identify the copper ligands. Bioinformatic analysis of the gene sequence and the sequences and contexts of neighboring genes suggested a tentative phylogenetic assignment to the genus Bacteroides. Kinetic, electrochemical, and EPR analyses provide unequivocal evidence that the hypothetical proteins from Bacteroides thetaiotaomicron and from E. coli, which are closely related to the deduced protein encoded by the RL5 gene, are also multicopper proteins with polyphenol oxidase activity. The present study shows that these three newly characterized enzymes form a new family of functional multicopper oxidases with laccase activity related to conserved hypothetical proteins harboring the domain of unknown function DUF152 and suggests that some other of these proteins may also be laccases.
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PMID:Novel polyphenol oxidase mined from a metagenome expression library of bovine rumen: biochemical properties, structural analysis, and phylogenetic relationships. 1674 Jun 38

Flavonoids are a big group of polyphenols of low molecular weight with in vitro antioxidant properties. In this study, the laccase and tyrosinase from Ustilago maydis were partially characterized and their effect on the antioxidant activity of some phenolic compounds was investigated. Since enzymatic polymerization of the phenolic compounds was detected, the size of the aggregates was determined and related to their antioxidant activity. Morphology of the polymers was analyzed by atomic force microscopy. The results showed that the laccase- and tyrosinase-catalyzed polymerization of quercetin produced aggregates with relatively low molecular weight and higher antioxidant activity than the monomeric quercetin. In the case of kaempferol, the aggregates reached higher sizes in the first 2 h of reaction and their antioxidant activity was increased. In the last case, the aggregates adopted fractal-ordered shapes similar to coral in the case of the kaempferol-laccase system and to fern in the case of the kaempferol-tyrosinase system. The kaempferol and quercetin polymers at low concentration had strong scavenging effect on Reactive oxygen species (ROS) and inhibition of lipoperoxidation in human hepatic cell line WRL-68.
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PMID:Enzymatic polymerization of phenolic compounds using laccase and tyrosinase from Ustilago maydis. 1676 6

Pseudomonas desmolyticum NCIM 2112 was able to degrade a diazo dye Direct Blue-6 (100 mg l(-1)) completely within 72 h of incubation with 88.95% reduction in COD in static anoxic condition. Induction in the activity of oxidative enzymes (LiP, laccase) and tyrosinase while decolorization in the batch culture represents their role in degradation. Dye also induced the activity of aminopyrine N-demethylase, one of the enzyme of mixed function oxidase system. The biodegradation was monitored by UV-Vis, IR spectroscopy and HPLC. The final products, 4-amino naphthalene and amino naphthalene sulfonic acid were characterized by GC-mass spectroscopy.
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PMID:Biodegradation of benzidine based dye Direct Blue-6 by Pseudomonas desmolyticum NCIM 2112. 1682 66

Oxidation of lignin obtained from acetosolv and ethanol/water pulping of sugarcane bagasse was performed by phenol oxidases: tyrosinase (TYR) and laccase (LAC), to increase the number of carbonyl and hydroxyl groups in lignin, and to improve its chelating capacity. The chelating properties of the original and oxidized lignins were compared by monitoring the amount of Cu2+ bound to lignin by gel permeation chromatography. The Acetosolv lignin oxidized with TYR was 16.8% and with LAC 21% higher than that of the original lignin. For ethanol/water lignin oxidized with TYR was 17.2% and with LAC 18% higher than that of the original lignin.
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PMID:Obtainment of chelating agents through the enzymatic oxidation of lignins by phenol oxidase. 1691 50

Ascomycetes that can deposit Mn(III, IV) oxides are widespread in aquatic and soil environments, yet the mechanism(s) involved in Mn oxide deposition remains unclear. A Mn(II)-oxidizing ascomycete, Acremonium sp. strain KR21-2, produced a Mn oxide phase with filamentous nanostructures. X-ray absorption near-edge structure (XANES) spectroscopy showed that the Mn phase was primarily Mn(IV). We purified to homogeneity a laccase-like enzyme with Mn(II) oxidase activity from cultures of strain KR21-2. The purified enzyme oxidized Mn(II) to yield suspended Mn particles; XANES spectra indicated that Mn(II) had been converted to Mn(IV). The pH optimum for Mn(II) oxidation was 7.0, and the apparent half-saturation constant was 0.20 mM. The enzyme oxidized ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] (pH optimum, 5.5; Km, 1.2 mM) and contained two copper atoms per molecule. Moreover, the N-terminal amino acid sequence (residues 3 to 25) was 61% identical with the corresponding sequence of an Acremonium polyphenol oxidase and 57% identical with that of a Myrothecium bilirubin oxidase. These results provide the first evidence that a fungal multicopper oxidase can convert Mn(II) to Mn(IV) oxide. The present study reinforces the notion of the contribution of multicopper oxidase to microbially mediated precipitation of Mn oxides and suggests that Acremonium sp. strain KR21-2 is a good model for understanding the oxidation of Mn in diverse ascomycetes.
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PMID:Manganese(IV) oxide production by Acremonium sp. strain KR21-2 and extracellular Mn(II) oxidase activity. 1702 Nov 94

Phenoloxidase activity was found in lichenized ascomycetes belonging to different taxonomic groups. Most of the epigeic and epilithic lichens of the order Peltigerales were found to possess both laccase and tyrosinase activities; the lichens of the order Lecanorales possessed only laccase activity, which was an order of magnitude lower than that of Peltigerales. Water-soluble phenoloxidases were present only in peltigerous lichens: activity that could be washed out from intact thalli comprised 10% of that released from disrupted thalli. The activity of the peltigerous lichens and the release of soluble phenoloxidases into the medium increased when the thalli were rehydrated quickly. In some of the lichens tested, the phenoloxidase activity was stimulated by desiccation-rehydration cycles. The oxidases discovered may play an important role in the phenolic metabolism of lichens and be involved in the biochemical reaction of humus synthesis during primary soil formation, which may be a previously unknown geochemical function of these symbiotic microorganisms.
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PMID:[Laccase and tyrosinase activities in lichens]. 1709 85

A pectolytic enzyme preparation from Aspergillus niger (pectinase AN) decreased most rutin content and antioxidant activity of asparagus juice. To investigate the mechanism of such loss, we analyzed several possible related enzyme activities in pectinase AN. We found that the activity of pectinase AN to oxidize guaiacol had no significant difference with or without the presence of H2O2; thus it was laccase activity, not peroxidase (PO) activity, that pectinase AN contained. We did not find any polyphenol oxidase (PPO) activity in pectinase AN. Laccase in pectinase AN could be the major cause of loss of rutin and antioxidant activity of asparagus juice. When most laccase activity of pectinase AN was inactivated after heating at 70 degrees C for 1.5 min and incubated with asparagus juice, the loss rate of rutin was only 9% of that treated with unheated pectinase AN, and the antioxidant activity was even increased. Rhamnosidase activity was detected in pectinase AN and can change rutin in asparagus juice to quercetin-3-glucoside, which has higher antioxidant activity than rutin. This may explain the increase of antioxidant activity of asparagus juice treated with heated pectinase AN that still contained some rhamnosidase activity. The discovery of our research is helpful to produce juice with high antioxidant activity and high health benefits in the juice industry.
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PMID:Enzyme-catalyzed change of antioxidants content and antioxidant activity of asparagus juice. 1719 13

Selective hydroxylation of aromatic compounds is among the most challenging chemical reactions in synthetic chemistry and has gained steadily increasing attention during recent years, particularly because of the use of hydroxylated aromatics as precursors for pharmaceuticals. Biocatalytic oxygen transfer by isolated enzymes or whole microbial cells is an elegant and efficient way to achieve selective hydroxylation. This review gives an overview of the different enzymes and mechanisms used to introduce oxygen atoms into aromatic molecules using either dioxygen (O(2)) or hydrogen peroxide (H(2)O(2)) as oxygen donors or indirect pathways via free radical intermediates. In this context, the article deals with Rieske-type and alpha-keto acid-dependent dioxygenases, as well as different non-heme monooxygenases (di-iron, pterin, and flavin enzymes), tyrosinase, laccase, and hydroxyl radical generating systems. The main emphasis is on the heme-containing enzymes, cytochrome P450 monooxygenases and peroxidases, including novel extracellular heme-thiolate haloperoxidases (peroxygenases), which are functional hybrids of both types of heme-biocatalysts.
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PMID:Enzymatic hydroxylation of aromatic compounds. 1722 Nov 66

Saccharomyces cerevisiae MTCC 463 decolourizes toxic azo dye, methyl red by degradation process. Methyl red (100mgl(-1)) is degraded completely within 16min in plain distilled water under static anoxic condition, at the room temperature. Effect of physicochemical parameters (pH of medium, composition of medium, concentration of cells, concentration of dye, temperature and agitation) on methyl red decolourization focused the optimal condition required for decolourization. Biodegradation (fate of metabolism) of methyl red in plain distilled water was found to be pH dependent. Cells of Saccharomyces cerevisiae could degrade methyl red efficiently up to 10 cycles in plain distilled water. Analysis of samples extracted with ethyl acetate from decolourized culture flasks in plain distilled water (pH 6.5) and at pH 9 using UV-VIS, TLC, HPLC and FTIR confirm biodegradation of methyl red into several different metabolites. A study of the enzymes responsible for the biodegradation of methyl red in the control and cells obtained after decolourization in plain distilled water (pH 6.5) and at pH 9 showed different levels of the activities of laccase, lignin peroxidase, NADH-DCIP reductase, azoreductase, tyrosinase and aminopyrine N-demethylase. A significant increase in the activities of lignin peroxidase and NADH-DCIP reductase was observed in the cells obtained after decolourization in plain distilled water (pH 6.5), however cells obtained at pH 9 shows increased activities of azoreductase, tyrosinase, lignin peroxidase and NADH-DCIP reductase. High efficiency to decolourize methyl red in plain distilled water and low requirement of environmental conditions enables this yeast to be used in biological treatment of industrial effluent containing azo dye, methyl red.
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PMID:Decolourization of azo dye methyl red by Saccharomyces cerevisiae MTCC 463. 1729 52

Laccase was detected in the culture filtrate of white-rot fungus Termitomyces clypeatus. The enzyme was found at the late phase of submerged growth in a medium containing glucose or cellulose as the carbon source. The present study indicates that laccase produced by T. clypeatus is an intracellular enzyme, released in the medium due to cell lysis at the end of the growing phase. Laccase produced by T. clypeatus is different from the extracellular polyphenol oxidase of T. albuminosus, also produced at the late phase of growth. This is the first report of laccase production by a Termitomyces sp.
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PMID:Laccase production by the white-rot fungus Termitomyces clypeatus. 1744 Sep 14


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