Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.2 (NQO1)
 6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxygen activation during oxidation of the lignin-derived hydroquinones 2-methoxy-1,4-benzohydroquinone (MBQH(2)) and 2, 6-dimethoxy-1,4-benzohydroquinone (DBQH(2)) by laccase from Pleurotus eryngii was examined. Laccase oxidized DBQH(2) more efficiently than it oxidized MBQH(2); both the affinity and maximal velocity of oxidation were higher for DBQH(2) than for MBQH(2). Autoxidation of the semiquinones produced by laccase led to the activation of oxygen, producing superoxide anion radicals (Q(*-) + O(2) <--> Q + O(2)(*-)). As this reaction is reversible, its existence was first noted in studies of the effect of systems consuming and producing O(2)(*-) on quinone formation rates. Then, the production of H(2)O(2) in laccase reactions, as a consequence of O(2)(*-) dismutation, confirmed that semiquinones autoxidized. The highest H(2)O(2) levels were obtained with DBQH(2), indicating that DBQ(*-) autoxidized to a greater extent than did MBQ(*-). Besides undergoing autoxidation, semiquinones were found to be transformed into quinones via dismutation and laccase oxidation. Two ways of favoring semiquinone autoxidation over dismutation and laccase oxidation were increasing the rate of O(2)(*-) consumption with superoxide dismutase (SOD) and recycling of quinones with diaphorase (a reductase catalyzing the divalent reduction of quinones). These two strategies made the laccase reaction conditions more natural, since O(2)(*-), besides undergoing dismutation, reacts with Mn(2+), Fe(3+), and aromatic radicals. In addition, quinones are continuously reduced by the mycelium of white-rot fungi. The presence of SOD in laccase reactions increased the extent of autoxidation of 100 microM concentrations of MBQ(*-) and DBQ(*-) from 4.5 to 30.6% and from 19.6 to 40.0%, respectively. With diaphorase, the extent of MBQ(*-) autoxidation rose to 13.8% and that of DBQ(*-) increased to 39.9%.
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PMID:Oxygen activation during oxidation of methoxyhydroquinones by laccase from Pleurotus eryngii. 1061 19

Extracellular hydroxyl radical ((*)OH) production via quinone redox cycling in Trametes versicolor, grown in a chemically defined medium, was investigated to degrade trichloroethylene (TCE), perchloroethylene (PCE), 1,2,4- and 1,3,5-trichlorobenzene (TCB). The activity of the enzymes catalyzing the quinone redox cycle, quinone reductase and laccase, as well as the rate of (*)OH production, estimated as the formation of thiobarbituric acid reactive substances (TBARS) from 2-deoxyribose, increased rapidly during the first 2-3 days and then remained at relatively constant levels. Under quinone redox cycling conditions, TCE degradation was concomitant to TBARS production and chloride release, reaching a plateau after 6 h of incubation. Similar results were obtained in PCE, 1,2,4- and 1,3,5-TCB time course degradation experiments. The mole balance of chloride release and 1,2,4-TCB and TCE degraded suggests that these chemicals were almost completely dechlorinated. Experiments using [(13)C]-TCE confirmed unequivocal transformation of TCE to (13)CO(2). These results are of particular interest because PCE and 1,3,5-TCB degradation in aerobic conditions has been rarely reported to date in bacterial or fungal systems.
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PMID:Induction of hydroxyl radical production in Trametes versicolor to degrade recalcitrant chlorinated hydrocarbons. 1961 36

Dihydrolipoamide dehydrogenase (LPD), a useful biocatalyst for regenerating NAD(+), was purified from Microbacterium luteolum JCM 9174, and the gene encoding LPD was cloned from the genomic DNA. The gene contained an opening reading frame consisting of 1395 nucleotides encoding 465 amino acid residues with a predicted molecular weight of 49912.1 Da, which displayed 36-78% homology to known LPDs. Moreover, the FAD- and NAD(+)-binding sites and the two catalytic residues in the LPDs were conserved. The enzyme was expressed in recombinant Escherichia coli cells and purified to homogeneity by column chromatography. LPD of M. luteolum (MluLPD) accepted not only lipoamide but also some artificial electron acceptors such as dichlorophenolindophenol (DCIP) and nitrotetrazolium blue (NTB), that is, it functions as a diaphorase. NAD(+) demonstrated a strong activating effect on MluLPD, and the activity was 5.2 times higher than that without NAD(+). The enzyme was suitable for regenerating NAD(+) in biocatalytic reactions because of its high affinity for NADH (6.1 microM). An NAD(+)-regenerating system with MluLPD and laccase using 2,5-dimethoxy-1,4-benzoquinone as a hydrogen acceptor was demonstrated.
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PMID:Gene cloning and characterization of dihydrolipoamide dehydrogenase from Microbacterium luteolum: A useful enzymatic regeneration system of NAD+ from NADH. 2015 66

Advanced oxidation of benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) by the extracellular hydroxyl radicals (*OH) generated by the white-rot fungus Trametes versicolor is for the first time demonstrated. The production of *OH was induced by incubating the fungus with 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe3+-EDTA. Under these conditions, *OH were generated through DBQ redox cycling catalyzed by quinone reductase and laccase. The capability of T. versicolor growing in malt extract medium to produce *OH by this mechanism was shown during primary and secondary metabolism, and was quantitatively modulated by the replacement of EDTA by oxalate and Mn2+ addition to DBQ incubations. Oxidation of BTEX was observed only under *OH induction conditions. *OH involvement was inferred from the high correlation observed between the rates at which they were produced under different DBQ redox cycling conditions and those of benzene removal, and the production of phenol as a typical hydroxylation product of *OH attack on benzene. All the BTEX compounds (500 microM) were oxidized at a similar rate, reaching an average of 71% degradation in 6 h samples. After this time oxidation stopped due to O2 depletion in the closed vials used in the incubations.
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PMID:Advanced oxidation of benzene, toluene, ethylbenzene and xylene isomers (BTEX) by Trametes versicolor. 2062 9