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

---

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

1. The inducible and constitutive forms of laccase from the fungus Pholiota mutabilis show both the oxidative and demethylating activity, which proves the bifunctional character of the enzyme. 2. The oxidative/demethylating activity ratio of the forms induced either with ferulic or syringic acid is different from that shown by the constitutive form. 3. Splitting of one methoxyl group from the methoxyphenol substrate is associated with the release of one molecule of methanol.
...
PMID:Oxidative and demethylating activity of multiple forms of laccase from Pholiota mutabilis. 12 Oct 8

The phenoloxidase system responsible for the sclerotization of cockroach ootheca is found to be present as an inactive form in the left colleterial gland of Periplaneta americana. The supernatant fraction obtained by centrifugation of the milky white secretions contained the inactive phenoloxidase which required both sodium dodecyl sulfate (SDS) and the insoluble sediment for exhibiting enzyme activity. Bovine serum albumin could replace the sediment in the activation process. Proteins separated from the supernatant fraction by molecular sieve chromatography on Sephadex G-25 did not require either albumin or the sediment, but required SDS for exhibiting the phenoloxidase activity. Among the detergents tested, SDS (anionic) and cetylpyridinium chloride (cationic) activated the phenoloxidase, but CHAPS (zwitterionic) or nonionic detergents failed to activate the enzyme. The activation caused by SDS occurred well below the critical micellar concentration of SDS indicating that SDS is causing the activation by binding to the protein and altering its conformation. Chloroform-methanol extracts of vestibulum or right gland could replace SDS confirming the presence of endogenous activator(s) of phenoloxidase system. A variety of exogenously added lipids could activate the latent enzyme, among which linoleate, oleate, laurate, linolenate, phosphatidylethanolamine, and phosphatidylglycerol proved to be the effective activators of the latent phenoloxidase. Partially purified phenoloxidase was found to be extremely labile and lost its activity on a) freezing and thawing, b) dialysis, and c) heating for 10 min at 55 degrees C. It exhibited a pH optimum of 7 and was inhibited drastically by phenylthiourea and diethyldithiocarbamate. It readily oxidized a number of o-diphenols such as 3,4-dihydroxybenzylalcohol, 3,4-dihydroxyphenethyl alcohol, catechol, N-acetyldopamine, N-acetylnorepinephrine, dopa, dopamine, etc., but failed to oxidize both 3,4-dihydroxybenzoic acid and 3,4-dihydroxybenzaldehyde. It neither converted the typical laccase substrate syringaldazine to its quinone methide product, nor oxidized the p-diphenols, hydroquinone and methylhydroquinone. Therefore, the enzyme participating in the quinone tanning of cockroach ootheca appears to be a typical o-diphenol oxidase and not a laccase as previously thought.
...
PMID:On the latency and nature of phenoloxidase present in the left colleterial gland of the cockroach Periplaneta americana. 213 24

Lignin peroxidase oxidizes non-phenolic substrates by one electron to give aryl-cation-radical intermediates, which react further to give a variety of products. The present study investigated the possibility that other peroxidative and oxidative enzymes known to catalyse one-electron oxidations may also oxidize non-phenolics to cation-radical intermediates and that this ability is related to the redox potential of the substrate. Lignin peroxidase from the fungus Phanerochaete chrysosporium, horseradish peroxidase (HRP) and laccase from the fungus Trametes versicolor were chosen for investigation with methoxybenzenes as a homologous series of substrates. The twelve methoxybenzene congeners have known half-wave potentials that differ by as much as approximately 1 V. Lignin peroxidase oxidized the ten with the lowest half-wave potentials, whereas HRP oxidized the four lowest and laccase oxidized only 1,2,4,5-tetramethoxybenzene, the lowest. E.s.r. spectroscopy showed that this congener is oxidized to its cation radical by all three enzymes. Oxidation in each case gave the same products: 2,5-dimethoxy-p-benzoquinone and 4,5-dimethoxy-o-benzoquinone, in a 4:1 ratio, plus 2 mol of methanol for each 1 mol of substrate. Using HRP-catalysed oxidation, we showed that the quinone oxygen atoms are derived from water. We conclude that the three enzymes affect their substrates similarly, and that whether an aromatic compound is a substrate depends in large part on its redox potential. Furthermore, oxidized lignin peroxidase is clearly a stronger oxidant than oxidized HRP or laccase. Determination of the enzyme kinetic parameters for the methoxybenzene oxidations demonstrated further differences among the enzymes.
...
PMID:Comparison of lignin peroxidase, horseradish peroxidase and laccase in the oxidation of methoxybenzenes. 216 14

A cDNA coding for laccase was isolated from the ligninolytic fungus Trametes versicolor by RNA-PCR. The cDNA corresponds to the gene lcc1, which encodes a laccase isoenzyme of 498 amino-acid residues preceded by a 22-residue signal peptide. The lcc1 cDNA was cloned into the vector pHIL-D2 for expression in Pichia pastoris under the control of the AOX1 promoter. Transformants were found to secrete active recombinant enzyme after induction with methanol. The use of growth medium buffered to pH 6.0 and control of pH during cultivation were found to be important, or even necessary, for obtaining activity in liquid cultures. The effect of exchanging the native secretion signal for the Saccharomyces cerevisiae alpha-factor pre-pro secretion signal was studied by cloning the portion encoding the mature enzyme into the vector pPIC9. The activity obtained for the construct encoding the native laccase signal sequence was found to be seven-fold higher than for the construct encoding the alpha-factor secretion signal. Utilisation of the P. pastoris pep4 mutant strain SMD1168 was found to provide a two-fold higher level of activity compared with P. pastoris GS115.
...
PMID:Laccase from the white-rot fungus Trametes versicolor: cDNA cloning of lcc1 and expression in Pichia pastoris. 938 99

Improved expression of recombinant laccase by Pichia pastoris carrying the lcc1 cDNA isolated from Trametes versicolor was achieved by optimization of the cultivation conditions in a fermentor equipped with a methanol sensor system. The results indicated that the activity obtained in fermentor cultivations was at least 7 times higher than in shake-flask cultures. Three different strategies for fermentor cultivations were compared: A (30 degrees C, 1.0% methanol), B (20 degrees C, 1.0% methanol), and C (20 degrees C, 0.5% methanol). The laccase activity, particularly the specific activity, could be improved by decreasing the cultivation temperature. The mechanisms behind the temperature effect on the laccase activity may be ascribed to poor stability, release of more proteases from dead cells, and folding problems at higher temperature. The results showed that the methanol concentration had a marked effect on the production of active heterologous laccase. A fivefold higher volumetric laccase activity was obtained when the methanol concentration was kept at 0.5% instead of 1.0%. The detrimental effect of methanol on the production of recombinant laccase may be attributed to lower laccase stability, a higher proteolytic activity, and folding problems due to higher growth rate at 1.0% methanol.
...
PMID:Fermentation strategies for improved heterologous expression of laccase in Pichia pastoris. 1211 7

Enzyme treatment is currently considered for remediation of terrestrial systems polluted with organic compounds. In this study, two soils from Pennsylvania with 2.8 or 7.4% organic matter contents (Soils 1 and 2, respectively) were amended with 14C-labeled 2,4-dichlorophenol (2,4-DCP) and incubated with a laccase from Trametes villosa (free or immobilized on montmorillonite). 2,4-DCP was either transformed to methanol-soluble polymeric products (11-32%) or covalently bound to soil organic matter (53-85%); unaltered 2,4-DCP could be recovered from soil by methanol extraction (0-38%) at the completion of a 14-d incubation period. In Soil 1, both free and immobilized laccase removed 100% of 2,4-DCP without regard for moisture conditions. In Soil 2, immobilized laccase removed more 2,4-DCP (about 95%, regardless of moisture conditions) than free enzyme (55, 75, and 90% at 30, 55, and 100% of maximum water-holding capacity, respectively). Binding of 2,4-DCP in the humin fraction was nearly the same for free and immobilized laccase. More 2,4-DCP, however, was bound to humic and fulvic acids in the presence of immobilized laccase than in the presence of free laccase. In general, immobilized laccase performed better than free laccase. However, for practical applications, the higher activity of immobilized laccase is offset by a 23% loss in enzyme activity during immobilization, which approximates the 30% increase in free laccase needed to achieve the same level of remediation. Furthermore, immobilized laccase is more costly than free T. villosa laccase.
...
PMID:Treatment of 2,4-dichlorophenol polluted soil with free and immobilized laccase. 1237 Nov 68

The Psc lac4 gene from Pleurotus sajor-caju has been cloned and expressed in the heterologous host Pichia pastoris, under the control of the AOX1 methanol inducible promoter. The native Ple. sajor-caju laccase signal sequence was effective in directing the secretion of lac4 expressed in Pic. pastoris. The control of media pH and temperature was found to be important in obtaining sufficient quantities of the protein to allow purification and subsequent biochemical characterization. The recombinant Psc Lac4 was purified to electrophoretic homogeneity and was shown to be immunologically related to Pleurotus eryngii Lac1. The purified laccase was estimated to have a molecular mass of around 59 kDa, to have a carbohydrate content of approximately 7% and a calculated pI of 4.38. The enzyme oxidized the substrates 2,2-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), 2,6-dimethoxyphenol, syringaldazine and guaiacol, exhibiting optimal pHs of 3.3, 6, 6.5 and 7 respectively. With ABTS as substrate the enzyme displayed optimal activity at 35 degrees C and pH 3.5. The enzyme was strongly inhibited by sodium azide and thioglycolic acid but not by EDTA.
...
PMID:Molecular cloning of a laccase isozyme gene from Pleurotus sajor-caju and expression in the heterologous Pichia pastoris host. 1248 Sep 4

Phenolic compounds originating from plant residue decomposition or microbial metabolism form humic-like polymers during oxidative coupling reactions mediated by various phenoloxidases or metal oxides. Xenobiotic phenols participating in these reactions undergo either polymerization or binding to soil organic matter. Another effect of oxidative coupling is dehalogenation, decarboxylation or demethoxylation of the substrates. To investigate these phenomena, several naturally occurring and xenobiotic phenols were incubated with various phenoloxidases (peroxidase, laccase, tyrosinase) or with birnessite (delta-MnO(2)), and monitored for chloride release, CO(2) evolution, and methanol or methane production. The release of chloride ions during polymerization and binding ranged between 0.2% and 41.4%. Using the test compounds labeled with 14C in three different locations (carboxyl group, aromatic ring, or aliphatic chain), it was demonstrated that 14CO(2) evolution was mainly associated with the release of carboxyl groups (17.8-54.8% of the initial radioactivity). Little mineralization of 14C-labeled aromatic rings or aliphatic carbons occurred in catechol, ferulic or p-coumaric acids (0.1-0.7%). Demethoxylation ranged from 0.5% to 13.9% for 2,6-dimethoxyphenol and syringic acid, respectively. Methylphenols showed no demethylation. In conclusion, dehalogenation, decarboxylation and demethoxylation of phenolic substrates appear to be controlled by a common mechanism, in which various substituents are released if they are attached to carbon atoms involved in coupling. Electron-withdrawing substituents, such as -COOH and -Cl, are more susceptible to release than electron-donating ones, such as -OCH(3) and -CH(3). The release of organic substituents during polymerization and binding of phenols may add to CO(2) production in soil.
...
PMID:Release of substituents from phenolic compounds during oxidative coupling reactions. 1273 92

Rutin, quercetin-3-rutinoside, is one of the most famous glycosides of flavonoid and widely present in many plants. In this study, we performed an oxidative polymerization of rutin using Myceliophthora laccase as catalyst in a mixture of methanol and buffer to produce a flavonoid polymer and evaluated antioxidant properties of the resultant polymer. Under selected conditions, the polymer with molecular weight of several thousands was obtained in good yields. The resulting polymer was readily soluble in water, DMF, and DMSO, although rutin monomer showed very low water solubility. UV measurement showed that the polymer had broad transition peaks around 255 and 350 nm in water, which were red-shifted in an alkaline solution. Electron spin resonance (ESR) measurement showed the presence of a radical in the polymer. The polymer showed greatly improved superoxide scavenging activity and inhibition effects on human low-density lipoprotein (LDL) oxidation initiated by 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH), compared with the rutin monomer. The polymer also protected endothelial cells from oxidative injury induced by AAPH as a radical generator with a much greater effect than the rutin monomer.
...
PMID:Enzymatic synthesis and antioxidant properties of poly(rutin). 1295 11

Laccase(EC1.10.3.2) can be used for enzymatic detoxification of lignocellulosic hydrolysates. By using molecular techniques such as RACE (rapid amplification of cDNA ends) and Genome-Walking, a laccase gene and its corresponding full-length cDNA were cloned from Flammulina velutipes and designated as glccFv and IccFv. The sequences were submitted to GenBank, and the accession numbers obtained were AY485826 and AY450406, respectively. Analysis of amino acids sequence suggested that one laccase from Polyporus ciliatus possessed the highest homology with the protein encoded by lccFv showing for 72%. The ORF (open reading frame) of lccFv was transformed into Pichia pastoris strain GS115 through the P. pastoris expression vector pHBM906, which contains both the promoter and transcription terminator of the AOX1 gene. The recombinant laccase LCCFv was detected from the engineering strain GS115 (pHBM557) which was fermented with BMMY liquid medium and induced by 1.0% (V/V) methanol at 20 degrees C with the highest expression level (0.1070 U/mL). The optimal reaction temperature of LCCFv that secreted from P. pastoris GS115(pHBM557) was 45 degrees C, the optimal reaction pH value was pH3.9 and the thermostability and pH stability were very well under the optimal conditions.
...
PMID:[Cloning of a laccase gene from Flammulina velutipes and study on its expression in Pichia pastoris]. 1611 Sep 59


1 2 3 4 5 6 7 Next >>

---