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)

This study was aimed at assessing the potential of the white-rot fungus Panus tigrinus CBS 577.79 in removing organic load, color and toxic phenols from agro-industrial effluent olive-mill wastewater (OMW). The influence of wastewater composition on P. tigrinus degradative capability was investigated in shaken cultures using two different OMWs. The initial soluble COD of 85,000 mg l(-1) led to a delay in removal of color, organic load and phenol by the fungus. This was associated with delayed onset of laccase and Mn-dependent peroxidase. On the other hand, P. tigrinus, when grown on OMW with an initial soluble COD content of 43,000 mg l(-1), promptly and efficiently removed the aforementioned components. Chromatographic analyses showed that 4-hydroxy-substituted simple phenols were predominantly removed. The polymeric aromatic fraction underwent simultaneous polymerization and depolymerization. This study is a contribution to the understanding of the degradative specificity of P. tigrinus on OMW aromatic components and provides good indications for possible future applications of the fungus.
Res Microbiol 2004 Sep
PMID:Panus tigrinus efficiently removes phenols, color and organic load from olive-mill wastewater. 1531 62

Previous studies on Melanocarpus albomyces laccase have shown that this enzyme is very interesting for both basic research purposes and industrial applications. In order to obtain a reliable and efficient source for this laccase, it was produced in the filamentous fungus Trichoderma reesei. Two approaches were used: production of a non-fused laccase and a hydrophobin-laccase fusion protein. Both proteins were expressed in T. reesei under the cbh1 promoter, and significantly higher activities were obtained with the non-fused laccase in shake-flask cultures (corresponding to about 230 mg l(-1)). Northern blot analyses showed rather similar mRNA levels from both expression constructs. Western analysis indicated intracellular accumulation and degradation of the hydrophobin-laccase fusion protein, showing that production of the fusion was limited at the post-transcriptional level. No induction of the unfolded protein response pathway by laccase production was detected in the transformants by Northern hybridization. The most promising transformant was grown in a fermenter in batch and fed-batch modes. The highest production level obtained in the fed-batch culture was 920 mg l(-1). The recombinant laccase was purified from the culture supernatant after cleaving the major contaminating protein, cellobiohydrolase I, by papain. The recombinant and wild-type laccases were compared with regard to substrate kinetics, molecular mass, pH optimum, thermostability, and processing of the N- and C-termini, and they showed very similar properties.
Microbiology (Reading) 2004 Sep
PMID:Expression of Melanocarpus albomyces laccase in Trichoderma reesei and characterization of the purified enzyme. 1534 64

Synthetic mesoporous alumina and silica minerals with uniform pore geometries, and their nonporous analogues, were used to test the role of mineral mesopores (2-50 nm diameter) in protecting organic matter from enzymatic degradation in soils and sediments. Dihydroxyphenylalanine (L-DOPA), a model humic compound, was irreversibly sorbed to both mineral types. The surface area-normalized adsorption capacity was greater for the mesoporous minerals relative to their nonporous analogues. The degradation kinetics of free and mineral-sorbed L-DOPA by the enzyme laccase was monitored in a closed cell via oxygen electrode. Relative to freely dissolved L-DOPA, nonporous alumina-sorbed substrate was degraded, on average, 90% more slowly and to a lesser extent (93%), likely due to laccase adsorption to alumina. In contrast, relative to free L-DOPA, degradation of nonporous silica-sorbed L-DOPA was enhanced by 20% on average. In the case of mesoporous alumina and silica-sorbed L-DOPA, the enzyme activity was 3-40 times lower than that observed for externally sorbed substrate (i.e., L-DOPA sorbed to nonporous minerals). These results provide strong evidence to support the viability of the mesopore protection mechanism for sequestration and preservation of sedimentary organic matter and organic contaminants. Nanopore adsorption/desorption phenomena may aid in explaining the slow degradation of organic contaminants in certain soils and sediments and may have implications for environmental remediation and biotechnological applications.
Environ Sci Technol 2004 Sep 01
PMID:Protection of mesopore-adsorbed organic matter from enzymatic degradation. 1546 Nov 61

Geotrichum-like strain R59, the anamorphic form of the white-rot fungus, Bjerkandera adusta, was isolated from soil. It was found to completely decolorize and degrade 10% daunomycin post-production effluent during 10 days of incubation at 26 degrees C. Strain R59 produced only low levels of ligninolytic enzymes when grown on wheat straw- or beech sawdust-containing media, but in the presence of humic acids derived from brown coal it synthesized significant amounts of laccase and lipase. This phenomenon was coupled with the fungus entering the idiophase and the appearance of aerial mycelium. B. adusta strain R59 was found to completely decolorize 0.03% humic acids from brown coal and lessive soil and to partially decolorize humic acids isolated from a chernozem during 14 days of growth. This ability of strain R59 could be useful in constructing a new generation of biologically active filters for the purification of humic acids-contaminated drinking waters.
Appl Microbiol Biotechnol 2005 Sep
PMID:Extracellular enzyme activities of Bjerkandera adusta R59 soil strain, capable of daunomycin and humic acids degradation. 1571 93

Electrochemical studies of laccases from basidiomycetes, i.e., Trametes hirsuta, Trametes ochracea, Coriolopsis fulvocinerea, Cerrena maxima, and Cerrena unicolor, have been performed. Direct (mediatorless) electrochemistry of laccases on graphite electrodes has been investigated with cyclic voltammetry, square wave voltammetry as well as potentiometry. For all mentioned high potential laccases direct electron transfer (DET) has been registered at spectrographic graphite and highly ordered pyrolytic graphite electrodes. The characteristics of DET reactions of the enzymes were analysed under aerobic and anaerobic conditions. It is shown that the T1 site of the laccase is the primary electron acceptor, both in solution (homogenous case) and at surface of the graphite electrode (heterogeneous case). A mechanism of ET for the process of the electro-reduction of oxygen at the laccase-modified graphite electrodes is proposed and the similarity of this heterogeneous process to the laccase catalysed oxygen reduction homogeneous reaction is concluded.
Bioelectrochemistry 2005 Sep
PMID:Direct electron transfer reactions of laccases from different origins on carbon electrodes. 1594 73

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.
J Biotechnol 2005 Sep 22
PMID:Cellobiose dehydrogenase formation by filamentous fungus Chaetomium sp. INBI 2-26(-). 1599 82

The present study investigated the ability of the non-pathogenic fungus Fusarium lateritium to either degrade or modify aromatic substances in olive-mill dry residue (DOR) and to reduce its phytotoxicity. The 80% reduction of ethylacetate extractable phenols in DOR colonized by the fungus for 20 weeks appeared to be due to polymerization reactions of phenol molecules as suggested by mass-balance ultrafiltration and size-exclusion chromatography experiments. Several lignin-modifying oxidases, including laccase, Mn-peroxidase and Mn-inhibited peroxidase were detected in F. lateritium solid-state cultures. Tests performed with tomato seedlings in soils containing 6% (w/w) sterilized non-inoculated DOR showed that the waste was highly phytotoxic. By contract, F. lateritium growth on DOR for 20 weeks led to a complete removal of the waste toxicity and to a higher shoot dry weight of tomato plants than that obtained in the absence of DOR.
Chemosphere 2005 Sep
PMID:Bioconversion of olive-mill dry residue by Fusarium lateritium and subsequent impact on its phytotoxicity. 1605 8

Multicopper blue proteins (MCBPs) are multidomain proteins that utilize the distinctive redox ability of copper ions. There are a variety of MCBPs that have been roughly classified into three different groups, based on their domain organization and functions: (i) nitrite reductase-type with two domains, (ii) laccase-type with three domains, and (iii) ceruloplasmin-type with six domains. Together, the second and third group are often commonly called multicopper oxidases (MCOs). The rapid accumulation of genome sequence information in recent years has revealed several new types of proteins containing MCBP domains, mainly from bacteria. In this review, the recent research on the functions and structures of MCBPs is summarized, mainly focusing on the new types. The latter half of this review focusses on the two domain MCBPs, which we propose as the evolutionary intermediate of the MCBP family.
Cell Mol Life Sci 2005 Sep
PMID:Function and molecular evolution of multicopper blue proteins. 1609 47

The ability to produce melanin is a key virulence factor in many fungal pathogens including the human basidiomycete pathogen Cryptococcus neoformans, a major cause of life-threatening infections among immunocompromised persons. Despite the significance of melanin biosynthesis in virulence of C. neoformans, the cellular and molecular processes involved in this pathway have not yet been fully elucidated. Here, we used Agrobacterium to isolate insertional mutants and screened 12 000 mutants to uncover genes involved in melanin production in C. neoformans. Four new mutant alleles of the well-known melanin biosynthesis gene, LAC1, which encodes laccase were identified, and the T-DNA was shown to have a possible predisposition for insertion into the promoters of genes, in particular LAC1. Melanization in C. neoformans is dependent on five additional genes identified in this screen encoding homologues of the copper transporter Ccc2, the copper chaperone Atx1, the chitin synthase Chs3, the transcriptional coactivator Mbf1 and the chromatin-remodelling enzyme Snf5. Illumination of the molecular and genetic components of this virulence pathway reveals potential novel targets for drug development against C. neoformans and provides further insight into the intimate relationship between metal ion homeostasis and melanin biosynthesis.
Mol Microbiol 2005 Sep
PMID:Novel gene functions required for melanization of the human pathogen Cryptococcus neoformans. 1610 7

Reliable screening methods are being demanded by biocatalysts' engineers, especially when some features such as activity or stability are targets to improve under non-natural conditions (i.e., in the presence of organic solvents). The current work describes a protocol for the design of a fungal laccase-expressed in Saccharomyces cerevisiae-highly active in organic cosolvents. A high-throughput screening assay based on ABTS (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) oxidation was validated. The stability of the ABTS radical cation was not significantly altered in the presence of acetonitrile, ethanol, or DMSO. With a coefficient of variance below 10% and a sensitivity limit of 15 pg laccase/microL, the assay was reproducible and sensitive. The expression system of Myceliophthora thermophila laccase variant T2 in S. cerevisiae was highly dependent on the presence of Cu2+. Copper concentration was limited up to 10 microM CuSO4 where expression levels (approximately 14-18 mg/L) were acceptable without compromising the reliability of the assay. A mutant library was created by error-prone PCR with 1.1 to 3.5 mutations per kb. After only 1 generation of directed evolution, mutant 6C9 displayed about 3.5-fold higher activities than parent type in the presence of 20% acetonitrile or 30% ethanol. The method provided here should be generally useful to improve the activity of other redox enzymes in mixtures of water/cosolvents.
J Biomol Screen 2005 Sep
PMID:Screening mutant libraries of fungal laccases in the presence of organic solvents. 1610 14


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