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)

Laccase is a copper-containing phenoloxidase, involved in lignin degradation by white rot fungi. The laccase substrate range can be extended to include nonphenolic lignin subunits in the presence of a noncatalytic cooxidant such as 2, 2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), with ABTS being oxidized to the stable cation radical, ABTS.+, which accumulates. In this report, we demonstrate that the ABTS.+ can be efficiently reduced back to ABTS by physiologically occurring organic acids such as oxalate, glyoxylate, and malonate. The reduction of the radical by oxalate results in the formation of H2O2, indicating the formation of O2.- as an intermediate. O2.- itself was shown to act as an ABTS.+ reductant. ABTS.+ reduction and H2O2 formation are strongly stimulated by the presence of Mn2+, with accumulation of Mn3+ being observed. Additionally, 4-methyl-O-isoeugenol, an unsaturated lignin monomer model, is capable of directly reducing ABTS.+. These data suggest several mechanisms for the reduction of ABTS.+ which would permit the effective use of ABTS as a laccase cooxidant at catalytic concentrations.
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PMID:Reduction of the 2,2'-Azinobis(3-ethylbenzthiazoline-6-sulfonate) cation radical by physiological organic acids in the absence and presence of manganese 960 10

Fourteen strains of white-rot basidiomycetes belonging to eight species of two genera (Inonotus and Pholiota) were tested for their ability to maintain the production of laccase, peroxidase and manganese-dependent peroxidase (enzymes involved in lignin biodegradation) after a short-time preservation in liquid nitrogen with different cryoprotectives (glycerol, dimethyl sulfoxide). No negative effect of cryopreservation or the used cryoprotective on production of the ligninolytic enzymes was found in the fungi tested.
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PMID:Activities of ligninolytic enzymes in some white-rot basidiomycete strains after recovering from cryopreservation in liquid nitrogen. 980 64

A basidiomycetous fungus Flavodon flavus (Klotzsch) Ryvarden (strain 312), isolated from decaying sea grass from a coral lagoon off the west coast of India, mineralized nearly 24% of 14C-labeled synthetic lignin to 14CO2 in 24 days. When grown in low-nitrogen medium (2.4 mM N) this fungus produced three major classes of extracellular lignin-modifying enzymes (LMEs): manganese-dependent peroxidase (MNP), lignin peroxidase (LIP), and laccase. Low MNP and laccase activities were seen in high-nitrogen medium (24 mM N), but no LIP activity was seen. In media containing lignocellulosic substrates such as pine, poplar, or sugarcane bagasse as the sole source of carbon and nitrogen, relatively high MNP and moderate levels of laccases were seen, but LIP production either was not seen or was minimal. LME production was also seen in media prepared with artificial seawater. Fast protein liquid chromatography and isoelectric focusing resolved LMEs into four isozymes each of MNP and LIP, while laccase isozymes were resolved into two groups, one group containing seven isozymes (pIs 4 to 6) and the other group containing at least three isozymes (pIs < 3). The molecular masses of the different isozymes were 43 to 99 kDa for MNP, 40 and 41.5 kDa for LIP, and 43 and 99 kDa for laccase. F. flavus showed effective degradation of various dye pollutants in media prepared with or without artificial seawater. This is the first report on the production of all three major classes of LMEs by F. flavus and points to the bioremediation potential of this organism in terrestrial as well as marine environments.
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PMID:Lignin-modifying enzymes of flavodon flavus, a basidiomycete isolated from a coastal marine environment 1022 7

Wheat straw cultures of the brown rot fungi Gloeophyllum striatum and G. trabeum degraded 2,4-dichlorophenol and pentachorophenol. Up to 54% and 27% 14CO2, respectively, were liberated from uniformly 14C-labeled substrates within 6 weeks. Under identical conditions Trametes versicolor, a typical white rot species employed as reference, evolved up to 42% and 43% 14CO2 and expressed high activities of laccase, manganese peroxidase, and manganese-independent peroxidase. No such activity could be detected in straw or liquid cultures of Gloeophyllum. Moreover, G. striatum degraded both chlorophenols most efficiently under non-cometabolic conditions, i.e. on a defined mineral medium lacking sources of carbon, nitrogen and phosphate.
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PMID:Degradation of 2,4-dichlorophenol and pentachlorophenol by two brown rot fungi. 1036 17

Fungal laccases are extracellular multinuclear copper-containing oxidases that have been proposed to be involved in ligninolysis and degradation of xenobiotics. Here, we show that an electrophoretically homogenous laccase preparation from the white rot fungus Trametes versicolor oxidized Mn2+ to Mn3+ in the presence of Na-pyrophosphate, with a Km value of 186 microM and a Vmax value of 0.11 micromol/min/mg protein at the optimal pH (5.0) and a Na-pyrophosphate concentration of 100 mM. The oxidation of Mn2+ involved concomitant reduction of the laccase type 1 copper site as usual for laccase reactions, thus providing the first evidence that laccase may directly utilize Mn2+ as a substrate.
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PMID:Novel enzymatic oxidation of Mn2+ to Mn3+ catalyzed by a fungal laccase. 1037 Nov 62

Under secondary metabolic conditions, the white-rot basidiomycete Coriolus versicolormetabolized 4-methyldibenzothiophene (MDBT), which is a recalcitrant organic sulfur contaminant found in petroleum. The pathway of the transformation of MDBT was elucidated by the identification of fungal metabolites upon the addition of MDBT and its metabolic intermediates. S-oxidation to form MDBT-5-oxide was the initial step of MDBT metabolism. Then, the metabolic pathway was branched to form MDBT-5-dioxide, which was a dead-end product, and hydroxymethylDBT (HMDBT)-5-oxide. Extracellular ligninolytic enzymes such as lignin and manganese peroxidases and laccase did not catalyze the oxidation of either MDBT or MDBT-5-oxide. HMDBT-5-oxide was then oxidized to HMDBT-5-dioxide. Piperonyl butoxide, an inhibitor of cytochrome P450, suppressed fungal oxidation of MDBT to its oxide, MDBT-5-oxide to dioxide and to HMDBT-5-oxide, and HMDBT-5-oxide to dioxide. The efficiency of the inhibition varied for each substrate, suggesting that each oxidation was catalyzed by different enzymes. The hydroxylation of methyl substituents to the hydroxymethyl group was suggested to be catalyzed by a novel monooxygenase. HMDBT-5-dioxide was finally xylosylated most likely by xylosyltrasferase to yield 10-(beta-D-xylopyranosyloxy)-4-methyldibenzothiophene-5-dioxide. The final xyloside product and metabolic intermediates are water-extractable compounds, which would give us a novel strategy for biodesulfurization technology.
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PMID:Bioconversion of recalcitrant 4-methyldibenzothiophene to water-extractable products using lignin-degrading basidiomycete coriolus versicolor 1044 62

Production of ligninolytic enzymes and degradation of 14C-ring labeled synthetic lignin by the white-rot fungus Cyathus stercoreus ATCC 36910 were determined under a variety of conditions. The highest mineralization rate for 14C dehydrogenative polymerizates (DHP; 38% 14CO2 after 30 days) occurred with 1 mM ammonium tartrate as nitrogen source and 1% glucose as additional carbon source, but levels of extracellular laccase and manganese peroxidase (MnP) were low. In contrast, 10 mM ammonium tartrate with 1% glucose gave low mineralization rates (10% 14CO2 after 30 days) but higher levels of laccase and manganese peroxidase. Lignin peroxidase was not produced by C. stercoreus under any of the studied conditions. Mn(II) at 11 ppm gave a higher rate of 14C DHP mineralization than 0.3 or 40 ppm, but the highest manganese peroxidase level was obtained with Mn(II) at 40 ppm. Cultivation in aerated static flasks gave rise to higher levels of both laccase and manganese peroxidase compared to the levels in shake cultures. 3,4-Dimethoxycinnamic acid at 500 microM concentration was the most effective inducer of laccase of those tested. The purified laccase was a monomeric glycoprotein having an apparent molecular mass of 70 kDa, as determined by calibrated gel filtration chromatography. The pH optimum and isoelectric point of the purified laccase were 4.8 and 3.5, respectively. The N-terminal amino acid sequence of C. stercoreus laccase showed close homology to the N-terminal sequences determined from other basidiomycete laccases. Information on C. stercoreus, whose habitat and physiological requirements for lignin degradation differ from many other white-rot fungi, expands the possibilities for industrial application of biological systems for lignin degradation and removal in biopulping and biobleaching processes.
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PMID:Production of ligninolytic enzymes and synthetic lignin mineralization by the bird's nest fungus Cyathus stercoreus. 1057 Aug 16

Ganoderma lucidum, a white rot basidiomycete widely distributed worldwide, was studied for the production of the lignin-modifying enzymes laccase, manganese-dependent peroxidase (MnP), and lignin peroxidase (LiP). Laccase levels observed in high-nitrogen (HN; 24 mM N) shaken cultures were much greater than those seen in low-nitrogen (2.4 mM N), malt extract, or wood-grown cultures and those reported for most other white rot fungi to date. Laccase production was readily seen in cultures grown with pine or poplar (100-mesh-size ground wood) as the sole carbon and energy source. Cultures containing both pine and poplar showed 5- to 10-fold-higher levels of laccase than cultures containing pine or poplar alone. Since syringyl units are structural components important in poplar lignin and other hardwoods but much less so in pine lignin and other softwoods, pine cultures were supplemented with syringic acid, and this resulted in laccase levels comparable to those seen in pine-plus-poplar cultures. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of concentrated extracellular culture fluid from HN cultures showed two laccase activity bands (M(r) of 40,000 and 66, 000), whereas isoelectric focusing revealed five major laccase activity bands with estimated pIs of 3.0, 4.25, 4.5, 4.8, and 5.1. Low levels of MnP activity ( approximately 100 U/liter) were detected in poplar-grown cultures but not in cultures grown with pine, with pine plus syringic acid, or in HN medium. No LiP activity was seen in any of the media tested; however, probing the genomic DNA with the LiP cDNA (CLG4) from the white rot fungus Phanerochaete chrysosporium showed distinct hybridization bands suggesting the presence of lip-like sequences in G. lucidum.
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PMID:Lignin-modifying enzymes of the white rot basidiomycete Ganoderma lucidum. 1058 81

The influence of aromatic compounds and Mn ions on activities of ligninolityc enzymes from white-rot fungus Pleurotus floridae has been studied. The specific inducers: vanillic acid and vanillyl alcohol--for activity of manganese-dependent peroxidase; vanillyl alcohol--for activity of cellobiose: quinone oxidoreductase during submerged, fermentation of Pleurotus floridae in Kirk's medium have been revealed. The inducers of laccase activity among studied aromatic compounds have not been revealed. The influence of Mn2+ in concentration range 0.4-68.4 mM on activities of ligninolytic enzymes of submerged culture of fungus P. floridae has been studied. Concentration of Mn ions 32.4 mM was optimal for manganese-dependent peroxidase activity.
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PMID:[Effect of aromatic compounds and Mn2+ on the ligninolytic enzyme complex from the fungus Pleurotus floridae (FRIES) Kummer--a white-rot wood fungus]. 1079 Oct 56

White-rot fungi (basidiomycetes) play an important role in the degradation of lignin which is, beside cellulose, the major compound of wood. This process is catalyzed by ligninolytic enzymes, which are able to cleave oxidatively aromatic rings in lignin structure. Manganese peroxidase and laccase of white-rot-fungi are the most important of these among the ligninolytic enzymes. In addition, they are able to degrade xenobiotic aromatic polymers, persisting as environmental pollutants. Manganese and aromatic compounds have often been discussed as being inducers, enhancers or mediators of these ligninolytic enzymes. It is known that supplementing the growth medium with either Mn2+, veratryl alcohol or coal-derived humic acids leads to significantly enhanced extracellular ligninolytic activities. Measuring the amount of expressed mRNA of the two enzymes by quantitative RT-PCR provided evidence that the expression of manganese peroxidase was induced in the three tested white-rot fungi, Clitocybula dusenii b11, Nematoloma frowardii b19, and a straw-degrading strain designated i63-2. Laccase, on the other hand, was expressed in all three fungi with a significant basic activity even without inducer added. However, since the level of laccase mRNA was higher in cultures supplemented with any one of the tested inducers, we conclude that both manganese and the aromatic substances also increase the expression of laccase.
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PMID:Differential expression of manganese peroxidase and laccase in white-rot fungi in the presence of manganese or aromatic compounds. 1113 96


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