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)

The system involved in the reduction of 2-[4'-di(2''-bromopropyl) aminophenylazolbenzoic acid (CB10-252), an agent designed for treating primary liver cell cancer, has been demonstrated to be localised mainly in the 108 000 X g supernatant fraction of rat liver homogenate. It is also present in other organs particularly in the spleen. DAB-azoreductase as shown previously is present almost entirely in the microsomal fraction and is found in high concentration only in liver. The pH maximum for CB10-252-azoreductase implying the importance of the 2'-carboxyl group in determining substrate specificity. The use of enzyme inhibitors and other additives showed that CB10-252 WAS NOT AXANTHINE OXIDASE OR DIHYDROFOLATE REDUCTASE. Its activity was not affected by carbon monoxide, phenobarbitone (PB), or 3-methylcholanthrene (MC) pretreatment. Enhancement of the activity by ferrous ions and FAD indicated that at least part of the reduction system could involve a flavoprotein with FAD as the prosthetic group. The activity of CB10-252-azoreductase and methylred-azoreductase was reduced by menadione (vitamin K3), cyanide and propylgallate. A diaphorase preparation from pig heart reduced both CB10-252 and methylred with both NADPH- and NADH-generating systems.
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PMID:Some characteristics of two azoreductase systems in rat liver. Relevance to the activity of 2-[4'-di(2"-bromopropyl)-aminophenylazo]benzoic acid (CB10-252), a compound possessing latent cytotoxic activity. 0 Jan 49

The activities of the cytochrome c reductases and of the D-T diaphorase in rat Leydig cell tumors have been described. The increase in enzymatic activity of the NADH cytochrome c reductase activity in functional tumors derived from interstitial cells of the rat testis is interpreted as being possibly related to hydroxylation of steroids by the neoplastic cells. Meanwhile, the increase in the activity of the D-T diaphorase in the other tumor is interpreted as being an anaplerotic reaction to substitute for the deficient shuttles for the transfer of reducing equivalents from the cytoplasm to the mitochondria observed in tumors.
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PMID:Dehydrogenation of reduced pyridine nucleotides by Leydig cell tumors of the rat testis. 0 36

The purified respiratory chain NADH dehydrogenase of Escherichia coli oxidizes NADH with either dichlorophenolindophenol (DCIP). ferricyanide, or menadione as electron acceptors, with values for NADH are similar with the three electron acceptors (approximately 50 muM). The purified enzyme contains no flavin and has an absolute requirement for FAD, with Km values around 4 muM. The pH optimum of the enzyme appears to be between 6.5 and 7; the optimum is difficult to establish because of nonenzymatic reduction of DCIP at the lower pH values. Potassium cyanide stimulates the DCIP reductase activity about 2-fold, but has no effect on ferricyanide reductase. The enzyme exhibits hyperbolic kinetics with respect to NADH concentration in both the ferricyanide and DCIP reductase assays, but cooperatively is seen in the menadione reductase reaction. NAD+ is an effective competitive inhibitor of the reaction (Ki congruent to 20 muM); in the presence of NAD+, the NADH saturation curve becomes cooperative, even in the DCIP reductase assay. Many adenine containing nucleotides are competitive inhibitors of the enzyme. The apparent Ki values for these nucleotides as inhibitors of the purified enzyme, the membrane-bound NADH dehydrogenase, and the NADH oxidase are equivalent. An examination of inhibitory effects of a series of adenine nucleotides suggests that the inhibitors act as analogues of NAD+, which is the true physiological inhibitor. The results suggest that the enzyme in situ is always partially inhibited by the levels of NAD- in the E coli cell, and thus behaves in a cooperative fashion to changes in the NAD+/NADH ratio. An antibody has been elicited against the purified NADH dehydrogenase. Immunodiffusion and crossed immunoelectrophoresis show that the antibody is directed principally against the NADH dehydrogenase, with some activity against minor contaminants in the purified preparation. The antibody inhibits NADH dehydrogenase activity 50% at saturating levels. When this antibody preparation is used to examine solubilized membrane preparations, two major immunoprecipitates are found. A parallel inhibition of the membrane-bound NADH dehydrogenase and NADH oxidase activities is seen, supporting the hypothesis that the purified enzyme is indeed a component of the respiratory chain-dependent NADH oxidase pathway.
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PMID:The NADH dehydrogenase of the respiratory chain of Escherichia coli. II. Kinetics of the purified enzyme and the effects of antibodies elicited against it on membrane-bound and free enzyme. 0 8

1. NADH-ubiquinone-1 and NADH-menadione reductase activities of Complex I were inhibited by diphenyleneiodonium (apparent Ki 23 and 30 nmol/mg of protein respectively). Reduction of K3Fe(CN)6 and juglone was relatively unaffected. 2. Iodoniumdiphenyl and derivatives were much less effective inhibitors. Compounds with similar ring structures to diphenyleneiodonium, in particular dibenzofuran, were inhibitors of NADH-ubiquinone-1 oxidoreductase. 3. Diphenylene[125I]iodonium specifically labelled a polypeptide of mol.wt. 23500. Maximum incorporation was 1 mol/mol of Complex-I flavin or 1 mol/mol of the 23500-mol.wt. polypeptide. 4. The label associated with this polypeptide was of limited stability, especially at lower pH. 5. Complete inhibition of ubiquinone reduction was achieved when 1 mol of inhibitor was incorporated/mol of Complex-I flavin, but the relationship between inhibition and labelling was not linear. 6. No evidence for covalent interaction between diphenyleneiodonium and the phospholipids of Complex I was obtained. 7. Rotenone increased the apparent affinity of diphenyleneiodonium for the 23500-mol.wt. polypeptide without affecting the maximum incorporation. 8. The 23500-mol.wt. polypeptide was not solubilized by chaotropic agents. Prior treatment of Complex I with chaotropic agents or sodium dodecyl sulphate prevented incorporation of diphenyleneiodonium into this polypeptide.
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PMID:Specific labelling of a constituent polypeptide of bovine heart mitochondrial reduced nicotinamide-adenine dinucleotide-ubiquinone reductase by the inhibitor diphenyleneiodonium. 1 40

Unlike Rhodospirillum rubrum, the highly purified preparations of NADP-reductase Thiocapsa roseopersicina are capable of reduction of cytochrome c though they do not catalyse diaphorase reaction in the presence of methyl viologen or benzyl viologen and NADH. T. roseopersicina reductase has more high temperature optimum (50-65 degrees) and more high thermal stability (65 degrees) and it is capable to catalyse diaphorase and menadione-reductase reactions under more high pH values (11.0-12.0) than NADP-reductase of R. rubrum. NADP-reductase of T. roseopersicina is more stable under storing than the enzyme from R. rubrum: the semi-inactivation period of the enzyme when storing in Ar or the air is about 10 and 4 days, respectively, and it takes about three days for R. rubrum.
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PMID:[Comparative study of NADP-reductase properties in two species of purple bacteria]. 2 Sep 91

Glutathione reductase (NAD(P)H: oxidized-glutathione oxidoreductase, EC 1.6.4.2) was purified to homogeneity from porcine erythrocytes by use of affinity chromatography on 2',5'-ADP-Sepharose 4-B. Analytical ultracentrifugation experiments were analysed to give the following physical parameters for the enzyme: s20,w = 5.7 S, D20,w = 50 microgram2/s, and Mw = 103 000 (protein concentration, 0.5 mg/ml). The frictional ratio was 1.37 and the Stokes radius was 4.3 nm. The enzyme molecule is a dimer composed of subunits of equal size each containing a FAD molecule. The amino acid compositions and circular dichroism spectra of the porcine and human enzymes indicated extensive structural similarities. The isoelectric point was at pH 6.85 (at 4 degrees C). The absorption spectrum of the oxidized enzyme had maxima at 377 and 462 nm. In vivo the enzyme appears to be partially reduced. At a physiological concentration of reduced glutathione the apparent Michaelis constants for glutathione disulfide and NADPH were higher than in the absence of reduced glutathione. At 0.15 M ionic strength the catalytic activity obtained with NADPH as reductant was optimal at pH 7 and more than 200 times higher than that obtained with NADH. S-sulfoglutathione and some mixed disulfides of glutathione were poor substrates with the exception of the mixed disulfide of coenzyme A and reduced glutathione. The purified enzyme displayed low transhydrogenase activity with oxidized pyridine nucleotide analogs and diaphorase activity with 2,6-dichlorophenolindophenol as acceptor substrates; both NADPH and NADH served as donors.
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PMID:Characterization of glutathione reductase from porcine erythrocytes. 3 12

This new assay procedure for diaphorase eliminates problems of high blank rates and nonlinear kinetics associated with other methods. The dye thiazolyl blue tetrazolium bromide is reduced in the presence of NADH and diaphorase to yield a colored formazan, which as maximum absorbance at 560 nm.
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PMID:A new assay for diaphorase activity in reagent formulations, based on the reduction of thiazolyl blue. 4 50

Frozen sections of eight odontogenic cysts, including one keratocyst, were incubated to show the following enzyme activities: NADH2 diaphorase, NADPH2 diaphorase, glucose-6-phosphate dehydrogenase, acid phosphatase and leucine aminopeptidase. The disbribution of lipid was shown by the oil red 0 method. The activities of all three oxidative enzymes were strongest in epithelial cells bordering hyalin bodies and in basal cells in the epithelial lining. Hydrolytic enzyme activity was absent from all but the most superficial epithelial cells but was present in macrophages and, in lesser amounts, in granular material in the same sections. The granular material frequently contained lipid. The lack of hydrolytic enzyme activity in bordering epithelial cells is inconsistent with the theory that hyalin bodies form from degenerating blood vessels. High aerobic oxidative enzyme activity in the same cells also conflicts with the concept that the bodies are a keratinous product. The findings lend support to the theory that hyalin bodies are an epithelial secretion.
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PMID:Enzyme histochemical studies on the formation of hyalin bodies in the epithelium of odontogenic cysts. 5 1

The case of a 35 years-old man, with chronic proximal muscle atrophy in which at the muscle biopsy tubular aggregates were found by histochemistry procedures is reported. The tubular aggregates stained positive with the modified Gomori trichrome, haematoxylin-eosin, DPNH-diaphorase, non specific esterases, phosphorylase, P.A.S., oil red O and lactate dehydrogenase. They did not show in the routine and acid pre-incubated ATPase, acid and alkaline phosphatases and succinate dehydrogenase. Only found in type II fibers. A brief discussion about the pathogenesis and function of the tubular aggregates is made. The authors believe that the tubular aggregates in this case are secondary to prolonged use of phenobarbital and diphenylhydantoin, associated with the basic denervation process and alcohol abuse.
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PMID:[Tubular aggregates in a case of chronic proximal spinal atrophy]. 8 34

Methemoglobinemia and mental retardation associated with NADH-diaphorase deficiency was found in a 2-year-old girl of Spanish origin. She showed no NADH-diaphorase activity in either erythrocytes or leukocytes, but electrophoretic studies of the hemolysate showed traces of an enzyme with normal mobility. Cytochrome b5 reductase activity was also found to be absent in the leukocytes of the propostius. Intermediate NADH-diaphorase activity was found in erythrocytes and leukocytes in her parents and her sister in accordance with the autosomal recessive mode of inheritance of this enzymopathy. The relationship between a generalized cytochrome b5 reductase deficiency and the progressive neurological involvement in our patient is discussed briefly.
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PMID:Congenital methemoglobin-reductase (cytochrome b5 reductase) deficiency associated with mental retardation in a Spanish girl. 9 93


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