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

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

The preparation of (R) and (S) [2(-3)H]lactate as well as (S) [2(-3)H] glutamate via the coupled exchange reaction catalyzed by NAD linked dehydrogenases and NADH: lipoamide oxidoreductase (diaphorase) is described. The specific radioactivity of the hydrogen ions of the 3HOH/H2O can be obtained in the substrates (100% exchange) if equilibrium isotope effects are disregarded. By the exchange procedure substrates with higher specific radioactivity are obtained from positionally [3H]labeled racemic mixtures prepared by chemical reductions with [3H]labeled hydrides. The tritium content of one of the enantiomeres is "washed out" into water. As examples are presented the preparation of (R) [2-3H] (S) [2-H]malate as well as the corresponding carnitine, glutamate and (R) and (S) lactate.
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PMID:Biochemical synthesis of stereospecifically hydrogen labeled compounds on a preparative scale, VI1-3 Synthesis of further substrates of NAD(P)-linked dehydrogenases of high specific tritium content. 12 62

Development of tumours of the urinarY bladder was studied in 59 Male and female Sprague-Dawley and Wistar rats with combined enzyme-histochemical and autoradiographic methods after oral application of n-butyl-n-(4-hydroxybutyl)-nitrosamine (BBN) and n-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT). as the first carcinogenic lesion detectable by light-microscopy a focal, sharply defined irreversible loss of alkaline phosphatase activity was consistently demonstrated in the urothelium, which appeared normal histologically and cytologically. In about 2/3 of the cases, NADH-diaphorase activity was markedly reduced in identical regions. The enzyme-deficient areas are to be considered as preneoplastic, because papillomas and carcinomas developed from them through different stages of hyperplasia. As a rule, these also were characterized by total loss of alkaline phosphatase activity and attenuation of the NADH-diaphorase in all parts or circumscribed areas. Autoradiographically 3H-thymidine-labelling index revealed a 43.2-fold (BBN) and 22.6-fold (FANFT) increase, respectively, in the enzyme-deficient areas, as compared with the surrounding emzyme-containing urothelium. After 54 hrs of continous labelling, there was a mean 3H-thymidine-labelling index of 54.9% in the enzyme-negative regions. The physiological mode of regeneration was no longer maintained in the areas of enzyme deficiency as there was an increased proliferation of suprabasal cells. Areas of papillomas that showed a marked attention of NADH-diaphorase had a 3H-thymidine-labelling index 4.5 (BBN) and 3.1 (FANFT) greater than the surrounding areas with preserved enzyme activity. Since loss of alkaline phosphatase activity occurs regulary and consistently after application of carcinogens with chemically different structures it appears to indicate the initial phase of tumor development in the urinary bladder of the rat.
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PMID:Focal loss of alkaline phosphatase and increase of proliferation in preneoplastic areas of the rat urothelium after administration of n-butyl-n-(4-hydroxybutyl)-nitrosamine and n-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide. 12 42


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