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)

Accelerated degradation of organic chemicals by aquatic plant-bacterial associations was reported for the first time with elucidation of the role and contribution of aquatic plant and bacteria in its rhizosphere using a fast-growing giant duckweed, Spirodela polyrrhiza. The results clearly showed the accelerated degradation of all the three aromatic compounds (phenol, aniline and 2,4-dichlorophenol [2,4-DCP]) tested by aquatic plant-bacterial associations. In phenol degradation system, phenol-degrading bacteria indigenous to the rhizosphere fraction of S. polyrrhiza mainly contributed, while in aniline degradation system S. polyrrhiza mainly contributed by stimulating aniline-degrading bacteria both in the rhizosphere and balk water fraction. On the other hand in 2,4-DCP degradation system, S. polyrrhiza itself mainly contributed to its removal by uptake and degradation. Thus, the mechanisms for accelerated removal of aromatic compounds were quite different depending on the substrates. S. polyrrhiza showed selective accumulation of phenol-degrading bacteria in its rhizosphere fraction, while aniline- and 2,4-DCP-degrading bacteria were not much accumulated. S. polyrrhiza secreted peroxidase and laccase. However, both of the enzymatic activities increased with the addition of aromatic compounds, degrading ability of S. polyrrhiza itself should be owing to the production of peroxidase rather than laccase because the change of peroxidase activity and concentration of each aromatic compound well concurred. From the results obtained in the present study, it can be concluded that the feasibility of the use of aquatic plant-bacterial associations to accelerate the degradation of organic chemicals especially recalcitrant compounds in aquatic environment was shown.
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PMID:Accelerated aromatic compounds degradation in aquatic environment by use of interaction between Spirodela polyrrhiza and bacteria in its rhizosphere. 1671 44

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

Seventeen non-allelic laccase genes and one gene footprint are present in the genome of Coprinopsis cinerea. Two gene subfamilies were defined by intron positions and similarity of deduced gene products, one with 15 members (lcc1-lcc15) and one with 2 members (lcc16, lcc17). The first subfamily divides in the phylogenetic tree of deduced proteins into smaller clusters that probably reflect recent gene duplication events. Different laccase genes diverged from each other both by frequent synonymous and non-synonymous codon changes. Mainly synonymous codon changes accumulate in alleles, with up to 12% total codon differences between given pairs of alleles. Overexpression of the 17 laccase genes under the control of a constitutive promoter identified nine active enzymes from subfamily 1. All of these showed laccase activities with DMP (2,6-dimethoxy phenol) as substrate but only eight of them also with ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)]. Lcc16 and Lcc17 share certain sequence features with ferroxidases but enzyme assays failed to show such activity. Lcc15 is expected to be non-functional in laccase activity due to an internal deletion of about 150 amino acids. Transcripts were obtained from all genes but splice junctions for three genes were not congruent with translation into a functional protein.
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PMID:The laccase multi-gene family in Coprinopsis cinerea has seventeen different members that divide into two distinct subfamilies. 1677 46

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

Laccases are phenol-oxidizing, multicopper enzymes produced by fungi, plants, insects and bacteria. Fungal laccases are involved in ecologically important processes such as decomposition of lignocellulose (wood and plant material). In this work, in order to find out the role of fungal laccases upon wood colonisation and lignin decay, we describe expression of laccase-encoding genes in the white rot basidiomycete Phlebia radiata 79, when the fungus grows on its natural substrates, that is on softwood (Alnus incana) and hardwood (Picea abies). Clones for two laccase-encoding genes, the previously described Pr-lac1 and a new gene Pr-lac2 were characterized. Pr-lac2 coding region is interrupted by 12 introns and the deduced Lac2 protein displays a higher pI value (5.8) than Lac1 (pI 3.2-3.5). Phylogenetic analysis indicates differential evolution for the two laccases, and Lac2 demonstrates the highest sequence identity with Trametes laccases (66%). Transcripts of Pr-lac1 were the most abundant both in solid-state softwood and semi-solid hardwood cultures, as analyzed by competitive RT-PCR and Northern hybridization. On spruce wood chips, Pr-lac1 and Pr-lac2 were expressed within 2-3 weeks of growth together with manganese and lignin peroxidase-encoding genes. Our results indicate wood-promoted but time-dependent regulation of expression for the two, at protein and gene level distinct P. radiata laccases.
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PMID:Expression and molecular properties of a new laccase of the white rot fungus Phlebia radiata grown on wood. 1692 90

The effect of various phenolic compounds on the activity of Rhus vernicifera laccase (Lc) has been evaluated using two different substrates, N,N-dimethyl-p-phenylenediamine and p-tert-butylcatechol. The observed effect strongly depends on the phenol employed and involves either a moderate activation, by halophenols, or inhibition, by acidic phenols. The collective data are consistent with an open active site in Lc, which is capable of accommodating more than one substrate or phenol molecule. According to NMR relaxation experiments, a phenol molecule binds at an average distance from type 1 Cu of about 6A, while evidence from electron paramagnetic resonance (EPR) experiments shows that binding of another phenol molecule induces a change, and probably occurs close to, the type 2/type 3 cluster. The effect of phenolic compounds on Lc reactivity is related to a modification of the substrate affinity for the enzyme. This affinity can either be increased, probably through pi-stacking or other types of interactions, or decreased, due to competition for the same site. In addition, the alteration induced in the trinuclear copper cluster has a marked effect on the enzyme reactivity. The inhibition observed with acidic phenols is probably due to the protonation of an enzyme intermediate produced at the trinuclear site, e.g. the peroxy intermediate, that causes the release of hydrogen peroxide and prevents the reaction of this intermediate with the substrate.
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PMID:Enzymatic and spectroscopic studies on the activation or inhibition effects by substituted phenolic compounds in the oxidation of aryldiamines and catechols catalyzed by Rhus vernicifera laccase. 1695 19

The phytotoxicity of olive-mill wastewater (OMW) has been suggested to be mainly due to its phenolic components. This study investigated the impact of three different low-cost dephenolization treatments on the wastewater phytotoxicity. To this aim, germinability of maize (Zea mays L.) seeds sown on a sandy-loamy soil which had been spread with different volumes (from 40 to 160m(3)ha(-1)) of either biologically-treated OMW or relative incubation control was determined. Biological treatments included either Panus tigrinus liquid cultures or incubation with commercial laccase (1UIml(-1)) or an innovative sequential combination of laccase and P. tigrinus cultures. All treatments markedly reduced phytotoxicity and promising results were obtained with commercial laccase. In fact, germinability and mean germination times in soil spread with laccase-treated OMW, did not significantly differ from those observed in soil irrigated with tap water (control) up to OMW volumes of 120m(3)ha(-1). Although the highest phenol reduction (ca. 81%) was obtained by the sequential use of laccase and P. tigrinus, the feasibility of the enzyme treatment is undoubtedly more convincing under the technological point of view.
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PMID:Enzyme and fungal treatments and a combination thereof reduce olive mill wastewater phytotoxicity on Zea mays L. seeds. 1700 5

The oxidation of aqueous phenol through the catalytic action of laccase from Trametes versicolor was studied over a wide range of phenol concentrations and enzyme activities. The stoichiometric ratio, which is defined as the molar ratio of phenol transformed to oxygen consumed in the catalytic reaction, was found to increase with phenol concentration in the reaction mixture from a theoretical lower limit of 1 and to approach a theoretical upper limit of 4. A logistic equation was proposed to relate reaction stoichiometry to substrate concentration and was successfully used to relate these parameters over a range of phenol concentrations extending from approximately 0.15 to 8 mM. This expression was incorporated into two kinetic models in order to account for variations in reaction stoichiometry during the reaction and to extend the range over which the models may be accurately applied. The new models demonstrated an improved ability to predict concentrations of phenol and oxygen over time in a closed batch reaction system.
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PMID:Variable stoichiometry during the laccase-catalyzed oxidation of aqueous phenol. 1731 88

Guaiacol, catechol, m-cresol are common phenolic compounds presented in various industrial effluents but difficult to be removed by conventional wastewater treatment schemes. To elucidate mechanisms of enhanced membrane removal by laccase polymerization, different MF and UF membranes were employed in a cross-flow module for phenol concentration of 5mM. With 2.98 IU/l of laccase applied at room temperature, guaiacol, catechol and m-cresol were polymerized to products of averaged molecular weight of 9600, 8350 and 5400 Da (Dalton), respectively. Methoxy and hydroxyl-substituted phenols (guaiacol and catechol) were polymerized better than methyl-substituted phenol (m-cresol) due to more stable free-radical containing intermediate structure induced by oxygen-containing methoxy and hydroxyl functional groups. Removal efficiencies for the un-reacted phenols were dependent on the molecular sizes (length and width), but were dependent on the molecular weight for the polymerized phenolic compounds. Flux was declined initially but reached steady state after 180 min of filtration, indicating these MF/UF membranes can be used for removal of these polymerized phenols without significant fouling. In addition, pretreatments by the inactivated laccase only caused further flux reduction without additional removal of phenols.
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PMID:Enhanced removal of three phenols by laccase polymerization with MF/UF membranes. 1760 Jul 3

The white-rot basidiomycete Physisporinus rivulosus strain T241i is highly selective for degradation of softwood lignin, which makes this fungus suitable for biopulping. In order to promote laccase production, P. rivulosus was cultivated in nutrient-nitrogen sufficient liquid media containing either charcoal or spruce sawdust as supplements. Two laccases with distinct pI values, Lac-3.5 and Lac-4.8, were purified from peptone-spruce sawdust-charcoal cultures of P. rivulosus. Both laccases showed thermal stability at up to 60 degrees C. Lac-4.8 was thermally activated at 50 degrees C. Surprisingly, both laccases displayed atypically low pH optima (pH 3.0-3.5) in oxidation of the commonly used laccase substrates syringaldazine (4-hydroxy-3,5-dimethoxybenzaldehyde azine), 2,6-dimethoxyphenol and guaiacol (2-methoxyphenol). Steady-state kinetic measurements pointed to unusually low affinity to guaiacol at low pH, whereas the kinetic constants for the methoxyphenols and ABTS were within the ranges reported for other fungal laccases. The combination of thermotolerance with low pH optima for methoxylated phenol substrates suggests that the two P. rivulosus T241i laccases possess potential for use in biotechnological applications.
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PMID:Novel thermotolerant laccases produced by the white-rot fungus Physisporinus rivulosus. 1780 27


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