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)

When glucose is the carbon source, the white rot fungus Pycnoporus cinnabarinus produces a characteristic red pigment, cinnabarinic acid, which is formed by laccase-catalyzed oxidation of the precursor 3-hydroxyanthranilic acid. When P. cinnabarinus was grown on media containing cellobiose or cellulose as the carbon source, the amount of cinnabarinic acid that accumulated was reduced or, in the case of cellulose, no cinnabarinic acid accumulated. Cellobiose-dependent quinone reducing enzymes, the cellobiose dehydrogenases (CDHs), inhibited the redox interaction between laccase and 3-hydroxyanthranilic acid. Two distinct proteins were purified from cellulose-grown cultures of P. cinnabarinus; these proteins were designated CDH I and CDH II. CDH I and CDH II were both monomeric proteins and had apparent molecular weights of about 81,000 and 101,000, respectively, as determined by both gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pI values were approximately 5.9 for CDH I and 3.8 for CDH II. Both CDHs used several known CDH substrates as electron acceptors and specifically adsorbed to cellulose. Only CDH II could reduce cytochrome c. The optimum pH values for CDH I and CDH II were 5.5 and 4.5, respectively. In in vitro experiments, both enzymes inhibited laccase-mediated formation of cinnabarinic acid. Oxidation intermediates of 3-hydroxyanthranilic acid served as endogenous electron acceptors for the two CDHs from P. cinnabarinus. These results demonstrated that in the presence of a suitable cellulose-derived electron donor, CDHs can regenerate fungal metabolites oxidized by laccase, and they also supported the hypothesis that CDHs act as links between cellulolytic and ligninolytic pathways.
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PMID:Novel interaction between laccase and cellobiose dehydrogenase during pigment synthesis in the white rot fungus Pycnoporus cinnabarinus. 992 58

The commonly used assay for measuring cellobiose dehydrogenase (CDH) activity, based on the reduction of dichlorophenol-indophenol (DCIP), has been adapted to measure this enzyme activity in the presence of laccase, which is often formed concurrently with CDH by a number of fungi. Laccase interferes with the assay by rapidly reoxidizing the reduced form of DCIP and can mask CDH activity completely. It can be conveniently and completely inhibited by 4 mM fluoride in the assay, while CDH activity is only slightly affected by the addition of this inhibitor. The modified assay enables the detection of low CDH activities even in the presence of very high excesses of laccase. It should be useful for screening culture supernatants of wood-degrading fungi for CDH since the assay is rapid and uses inexpensive and nontoxic reagents. Furthermore, it might be used for the detection of other enzyme activities which are assayed by following the reduction of quinones or analogue compounds such as DCIP.
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PMID:A simple assay for measuring cellobiose dehydrogenase activity in the presence of laccase. 1033 77

The growth of nonsporulating mycelial fungi INBI 2-26(+), producer of laccase; INBI 2-26(-), producer of cellobiose dehydrogenase; and their mixed culture on lignin-carbohydrate substrates under conditions of submerged fermentation were studied. The degrees of degradation of lignin, cellulose, and hemicellulose of cut straw over 23 days amounted to 29.8, 51.4, and 72% for the laccase producer; 15.8, 33.9, and 59.1% for the cellobiose dehydrogenase producer; and 15.8, 39.4, and 64.5% for the mixed culture, respectively. The laccase activity in the medium when strain 2-26(+) was cultivated individually reached its maximum on day 28; the activity of cellobiose dehydrogenase of strain 2-26(-), on days 14 to 28. A method for determining cellobiose dehydrogenase activity in the presence of laccase was developed. In the mixed culture, both enzymes were formed; however, the level of laccase synthesis was 1.5-fold lower compared to that of strain 2-26(+), while synthesis of cellobiose dehydrogenase was similar to that of the corresponding producer. Cellobiose dehydrogenase failed to boost the action of laccase while degrading the lignin of straw.
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PMID:[Degradation of lignin-carbohydrate substrate by soil fungi--producers of laccase and cellobiose dehydrogenase]. 1502 98

Pleurotus ostreatus (Florida), ITCC 3308 produces approximately 9.0 U/ml extracellular cellobiose dehydrogenase (CDH) in cellulose medium after 7 days of growth. However, no activity could be detected if the assay was done with cellobiose as the substrate and 2,6-dichlorophenol indophenol (DPIP) as the electron acceptor in absence of any laccase inhibitor. Kinetic study showed that V(max)/K(m) value was very high for rDPIP (reduced 2,6-dichlrophenol indophenol) oxidation by laccase. Oxygen consumption rate of rDPIP oxidation by the enzyme was found to be highest among all the tested substrates. The present study indicated that rDPIP was a good substrate for laccase. Therefore, caution is needed to measure CDH activity by monitoring DPIP reduction in a system where laccase is likely to be present.
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PMID:Interference of laccase in determination of cellobiose dehydrogenase activity of Pleurotus ostreatus (Florida) using dichlorophenol indophenol as the electron acceptor. 1581 59

During dye decoloration by Trametes versicolor ATCC 20869 in modified Kirk's medium, manganese peroxidase (MnP) and laccase were produced, but not lignin peroxidase, cellobiose dehydrogenase or manganese-independent peroxidase. Purified MnP decolorized azo dyes [amaranth, reactive black 5 (RB5) and Cibacron brilliant yellow] in Mn(2+)-dependent reactions but did not decolorize an anthraquinone dye [Remazol brilliant blue R (RBBR)]. However, the purified laccase decolorized RBBR five to ten times faster than the azo dyes and the addition of a redox mediator, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), did not alter decoloration rates. Amaranth and RB5 were decolorized the most rapidly by MnP since they have a hydroxyl group in an ortho position and a sulfonate group in the meta position relative to the azo bond. During a typical batch decoloration with the fungal culture, the ratio of laccase:MnP was 10:1 to 20:1 (based on enzyme activity) and increased to greater than 30:1 after decoloration was complete. Since MnP decolorized amaranth about 30 times more rapidly than laccase per unit of enzyme activity, MnP should have contributed more to decoloration than laccase in batch cultures.
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PMID:Contribution of manganese peroxidase and laccase to dye decoloration by Trametes versicolor. 1583 15

White-rot fungi (WRF) are ubiquitous in nature with their natural ability to compete and survive. WRF are the only organisms known to have the ability to degrade and mineralize recalcitrant plant polymer lignin. Their potential to degrade second most abundant carbon reserve material lignin on the earth make them important link in global carbon cycle. WRF degrade lignin by its unique ligninolytic enzymatic machinery including lignin peroxidase, manganese peroxidase, laccase, cellobiose dehydrogenase, H2O2-generating enzymes, etc. The ligninolytic enzymes system is non-specific, extracellular and free radical based that allows them to degrade structurally diverse range of xenobiotic compounds. Lignin peroxidase and manganese peroxidase carry out direct and indirect oxidation as well as reduction of xenobiotic compounds. Indirect reactions involved redox mediators such as veratryl alcohol and Mn2+. Reduction reactions are carried out by carboxyl, superoxide and semiquinone radicals, etc. Methylation is used as detoxification mechanism by WRF. Highly oxidized chemicals are reduced by transmembrane redox potential. Degradation of a number of environmental pollutants by ligninolytic system of white rot fungi is described in the present review.
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PMID:Degradation of xenobiotic compounds by lignin-degrading white-rot fungi: enzymology and mechanisms involved. 1587 13

Laccase-negative filamentous fungus INBI 2-26(-) isolated from non-sporulating laccase-forming fungal association INBI 2-26 by means of protoplast technique was identified as Chaetomium sp. based on partial sequence of its rRNA genes. In the presence of natural cellulose sources, the strain secreted neutral cellobiose dehydrogenase (CDH) activity both in pure culture and in co-culture with laccase-positive filamentous fungus INBI 2-26(+) isolated from the same association. INBI 2-26(-) also secreted CDH during submerged cultivation in minimal medium with glucose as the sole carbon source. Maximal CDH activity of 1IU/ml at pH 6 with 2,6-dichlorophenolindophenol (DCPIP) as an acceptor was obtained on 12th day of submerged cultivation with filter paper as major cellulose source. Cellulase system of Chaetomium sp. INBI 2-26(-) capable of adsorption onto H(3)PO(4)-swollen filter paper consisted of four major proteins (Mr 200, 95, 65 and 55K) based on SDS-polyacrylamide gel electrophoresis and was capable of DCPIP reduction without exogenous cellobiose.
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PMID:Cellobiose dehydrogenase formation by filamentous fungus Chaetomium sp. INBI 2-26(-). 1599 82

Amorphous cellulose was used as a specific carrier for the deposition of self-assembled multienzyme complexes capable of catalyzing coupled reactions. Naturally glycosylated fungal cellobiohydrolases (CBHs) of glycosyl hydrolase families 6 and 7 were specifically deposited onto the cellulose surface through their family I cellulose-binding modules (CBM). Naturally glycosylated fungal laccase was then deposited onto the preformed glycoprotein layer pretreated by ConA, through the interaction of mannosyl moieties of fungal glycoproteins with the multivalent lectin. The formation of a cellulase-ConA-laccase composite was proven by direct and indirect determination of activity of immobilized laccase. In the absence of cellulases and ConA, no laccase deposition onto the cellulose surface was observed. Finally, basidiomycetous cellobiose dehydrogenase (CDH) was deposited onto the cellulose surface through the specific interaction of its FAD domain with cellulose. The obtained paste was applied onto the surface of a Clark-type oxygen electrode and covered with a dialysis membrane. In the presence of traces of catechol or dopamine as mediators, the obtained immobilized multienzyme composite was capable of the coupled oxidation of cellulose by dissolved oxygen, thus providing the basis for a sensitive assay of the mediator. Swollen amorphous cellulose plays three different roles in the obtained biosensor as: (i) a gelforming matrix that captures the analyte and its oxidized intermediate, (ii) a specific carrier for protein self-assembly, and (iii) a source of excess substrate for a pseudo-reagent-less assay with signal amplification. The detection limit of such a tri-enzyme biosensor is 50-100 nM dopamine.
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PMID:Application of cellulose-based self-assembled tri-enzyme system in a pseudo-reagent-less biosensor for biogenic catecholamine detection. 1737 47

Dyes belonging to the mono-, di-, tri- and poly-azo as well as anthraquinonic and mono-azo Cr-complexed classes, chosen among the most utilized in textile applications, were employed for a comparative enzymatic decolorization study using the extracellular crude culture extracts from the white rot fungus Funalia (Trametes) trogii grown on different culture media and activators able to trigger different levels of expression of oxidizing enzymes: laccase and cellobiose dehydrogenase. Laccase containing extracts were capable to decolorize some dyes from all the different classes analyzed, whereas the recalcitrant dyes were subjected to the combined action of laccase and the chemical mediator HBT, or laccase plus cellobiose dehydrogenase. Correlations among the decolorization degree of the various dyes and their electronic and structural diversities were rationalized and discussed. The utilization of cellobiose dehydrogenase in support to the activity of laccase for the decolorization of azo textile dyes resulted in substantial increases in decolorization for all the refractory dyes proving to be a valid alternative to more expensive and less environmentally friendly chemical treatments of textile dyes wastes.
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PMID:Fungal laccase, cellobiose dehydrogenase, and chemical mediators: combined actions for the decolorization of different classes of textile dyes. 1828 Dec 11

The effect of bubble-free oxygenation on the stability of a bi-enzymatic system with redox mediator regeneration for the conversion of lactose to lactobionic acid was investigated in a miniaturized reactor with bubbleless oxygenation. Earlier investigations of this biocatalytic oxidation have shown that the dispersive addition of oxygen can cause significant enzyme inactivation. In the process studied, the enzyme cellobiose dehydrogenase (CDH) oxidizes lactose at the C-1 position of the reducing sugar moiety to lactobionolactone, which spontaneously hydrolyzes to lactobionic acid. 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt was used as electron acceptor for CDH and was continuously regenerated (reoxidized) by laccase, a blue multi-copper oxidase. Oxygen served as the terminal electron acceptor of the reaction and was fully reduced to water by laccase. The overall mass transfer coefficient of the miniaturized reactor was determined at 30 and 45 degrees C; conversions were conducted both in the reaction-limited and diffusion-limited regime to study catalyst inactivation. The bubbleless oxygenation was successful in avoiding gas/liquid interface inactivation. It was also shown that the oxidized redox mediator plays a key role in the inactivation mechanism of the biocatalysts unobserved during previous studies.
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PMID:Bubble-free oxygenation of a bi-enzymatic system: effect on biocatalyst stability. 1869 49


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