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:1.6.5.2 (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 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

The Neurospora crassa assimilatory NAD(P)H-nitrite reductase complex has associated a NAD(P)H-diaphorase activity. 1. This NAD(P)H-diaphorase activity can use either mammalian cytochrome c, 2,6--dichlorophenol-indophenol, ferricyanide, or menadione as electron acceptor from the reduced pyridine nucleotides, and requires flavin adenine dinucleotide for maximal activity. 2. It is inhibited by p-hydroxymercuribenzoate, 1 muM, and it is unaffected by cyanide, sulfite, or arsenite at concentrations which completely inhibit the NAD(P)H-nitrite reductase activity. 3. Flavin adenine dinucleotide specifically protects the NAD(P)H-diaphorase activities, but not the NAD(P)H-nitrite reductase activities, against thermal inactivation. 4. In vitro preincubation of the Neurospora crassa nitrite reductase complex with reduced pyridine nucleotides plus flavin adenine dinucleotide inactivates the NAD(P)H-nitrite reductase activities, but does not affect the NAD(P)H-diaphorase activities, indicating that this nitrite reductase inactivation occurs in the part of the enzyme that contain the nitrite reducing center.
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PMID:A reduced pyridine nucleotides-diaphorase activity associated to the assimilatory nitrite reductase complex from Neurospora crassa. 13 35

Addition of beta-lapachone, an o-naphthoquinone endowed with trypanocidal properties to respiring Trypanosoma cruzi epimastigotes induced the release of O2- and H2O2 from the whole cells to the suspending medium. The same beta-lapachone concentration (4 micron) that released H2O2 at maximal rate completely inhibited T. cruzi growth in a liquid medium. The position isomer, alpha-lapachone, did not stimulate O2- and H2O2 release, and did not inhibit epimastigote growth. beta-Lapachone was able to stimulate H2O2 production by the epimastigote homogenate in the presence of NADH as reductant. The same effect was observed with the mitochondrial fraction supplemented with NADH, where beta-lapachone enhanced the generation of O2- and H2O2 4.5- and 2.5-fold respectively. beta-Lapachone also increased O2- and H2O2 production (2.5 and 2-fold respectively) by the microsomal fraction with NADPH as reductant. Cyanide-insensitive NADH and NADPH oxidation by the mitochondrial and microsomal fractions (quinone reductase activity) was stimulated to about the same extent by beta-lapachone. alpha-Lapachone was unable to increase O2- and H2O2 production and quinone reductase activity of the mitochondrial and microsomal fractions.
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PMID:Effect of beta-lapachone on superoxide anion and hydrogen peroxide production in Trypanosoma cruzi. 21 40

The rabbits being repeatedly poisoned with small doses of sodium cyanide, the activity of succinic dehydrogenase in the tissues does not essentially change. The activity of NAD.H2-cytochrome-c-reductase and NAD.H2-diaphorase in the brain, myocardium and kidneys increases. Under histotoxic hypoxia the level of iron in the tissues increases by 52-93%, that of copper--by 28-36%, of zinc--by 21-74% and of cobalt by 28-40%. There existed a positive correlation between the content of iron and the activity of NAD-dependent enzymes. In nonlethal form of histotoxic hypoxia the content of nonhemin iron and the activity of NAD.H2-cytochrome-c-reductase in the mitochondria of the brain increases by 25% and 17%, respectively, and a direct correlation is revealed between them.
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PMID:[Iron, copper, zinc and cobalt content and activity of respiratory metalloenzymes in animal tissues under toxic hypoxia]. 68 69

L5178Y/HBM10 lymphoblasts, resistant to a model quinone antitumor agent, hydrolyzed benzoquinone mustard, were approximately 2-fold more sensitive to trenimon (2,3,5-tris-ethyleneimino-1,4-benzoquinone) compared to parental cells (L5178Y). The L5178Y/HBM10 cells are reported to have a 24-fold increased level of DT-diaphorase activity over the parental cells. Inhibition of DT-diaphorase by dicoumarol markedly inhibited the cytotoxic activity of trenimon to the resistant L5178Y/HBM10 cells. Spectrophotometric analysis of the reduction of the quinone, trenimon, to its hydroquinone form was shown to occur approximately 25 times more rapidly in the L5178Y/HBM10 cells relative to the parental cells and was inhibited by discoumarol. Trenimon also induced continuous cyanide-resistant respiration in the L5178Y cells, but not in the resistant L5178Y/HBM10 cells. This suggested a one-electron reduction of trenimon to a semiquinone free radical which could then redox cycle with oxygen in the L5178Y cells. However, in the presence of dicoumarol the resistant L5178Y/HBM10 cells induced similar oxygen activation to the parental cells. Dicoumarol had no effect on trenimon-induced cyanide resistant respiration in the parental cells. These findings suggest that the two-electron reduction of trenimon to its hydroquinone derivative plays a major role in the cytotoxic activity of trenimon.
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PMID:Molecular mechanisms of trenimon-induced cytotoxicity in resistant L5178Y/HBM10 cells. 137 87

Trenimon belongs to a class of aziridinylbenzoquinone anticancer drugs that cross the blood-brain barrier. In this study we have investigated the molecular mechanisms for trenimon-induced toxicity in aerobic versus hypoxic conditions with the use of freshly isolated rat hepatocytes. The following evidence suggests the mechanisms for trenimon detoxification involves reduction by DT-diaphorase, while the cytotoxic mechanism involves macromolecular alkylation under hypoxic conditions as well as oxidative stress under aerobic conditions. (a) Hepatocyte cytotoxicity induced by trenimon (250 microM) under aerobic conditions ensued following an initial induction of cyanide-resistant respiration and partial oxidation of glutathione to oxidized glutathione. Trenimon reduction to the hydroquinone by the hepatocytes was rapid. Inhibition of hepatocyte DT-diaphorase by dicumarol increased trenimon-induced cytotoxicity by approximately 10-fold, and markedly inhibited hydroquinone formation. Furthermore, both cyanide-resistant respiration and oxidized glutathione formation were markedly increased, resulting in depletion of oxygen in the media. Trenimon reduction to the hydroquinone then occurred. This suggests that DT-diaphorase in normal hepatocytes prevents the formation of the semiquinone that causes cytotoxic protein alkylation and oxidative stress. (b) Hepatocyte cytotoxicity induced by trenimon (350 microM) under hypoxic conditions ensued following glutathione depletion without oxidized glutathione formation. Inactivation of hepatocyte DT-diaphorase by dicumarol under hypoxic conditions increased trenimon-induced cytotoxicity by approximately 3.5-fold and increased semiquinone radical levels 2-fold without affecting its reduction rate. This suggests that the cytotoxic mechanism involves protein alkylation by semiquinone radicals formed by reductases catalyzing a one-electron reduction of trenimon.
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PMID:Modulation of trenimon-induced cytotoxicity by DT-diaphorase in isolated rat hepatocytes under aerobic versus hypoxic conditions. 137 32

Male and female C57Bl/6 mice were administered perfluor-octanoic acid PFOA; 0.02-0.05% w/w; 5-10 days) in their diet. This treatment resulted in a several-fold induction of hepatic peroxisomal fatty acid beta-oxidation (monitored as increases in cyanide-insensitive palmitoyl-CoA oxidation, lauroyl-CoA oxidase and catalase activity) in all animals. The protein content of the hepatic mitochondrial fraction was also increased in all mice exposed to PFOA. Furthermore, studies on xenobiotic-metabolizing enzymes revealed no sex-related difference in the response to PFOA. All mice demonstrated a dramatic increase in omega-hydroxylation of lauric acid. Cytosolic epoxide hydrolase, glutathione transferase and DT-diaphorase activities were increased about 2-5-fold. These results with mice differ dramatically from previous studies and our own experiments here with Wistar rats, in which exposure to PFOA causes hepatic peroxisome proliferation in male animals, whereas females are unaffected.
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PMID:The effects of perfluoro-octanoic acid on hepatic peroxisome proliferation and related parameters show no sex-related differences in mice. 149 16

Membranes of the green sulfur bacterium, Chlorobium limicola f. thiosulfatophilum, catalyze the reduction of externally added isoprenoid quinones by sulfide. This activity is highly sensitive to stigmatellin and aurachins. It is also inhibited by 2-n-nonyl-4-hydroxyquinoline-N-oxide, antimycin, myxothiazol and cyanide. It is concluded that in sulfide oxidizing bacteria like Chlorobium, sulfide oxidation involves a sulfide-quinone reductase (SQR) similar to the one found in Oscilatoria limnetica [Arieli, B., Padan, E. and Shahak, Y. (1991) J. Biol. Chem. 266, 104-111].
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PMID:Sulfide quinone reductase (SQR) activity in Chlorobium. 154 83

HepG2 cells were cultured in the presence of different concentrations of cyclosporin A (CsA) or Nva2-cyclosporin (Nva2-Cs) for up to 20 days. At a low concentration (2 micrograms/ml) of CsA or Nva2-Cs, the [3H]thymidine incorporation into DNA and the rate of incorporation of [3H]leucine into total protein decreased by 20-25%. Concentrations of 10 micrograms/ml resulted in a 70% reduction of the [3H]thymidine incorporation in comparison with controls. Low concentrations of CsA resulted in mitochondria in the condensed state together with autophagosomes, large vacuoles, and elevated numbers of coated vesicles, as shown by electron microscopy. Low concentrations of Nva2-Cs resulted in swollen mitochondria, increased autophagocytosis, and increased numbers of intermediate filaments and microtubules. Higher doses of these substances (5 micrograms/ml) caused disarrangement of mitochondrial cristae, vesiculation of the endoplasmic reticulum, an elevated number of free polysomes, and accelerated autophagocytosis. Labeling of phospholipids and triglycerides with [3H]glycerol and of cholesterol and dolichol with [3H]acetate was decreased after exposure of HepG2 cells to CsA, or, in particular, Nva2-Cs. Phospholipids secreted from the cells into the medium exhibited an increased level of labeling, but the specific radioactivity of the neutral lipids in the medium was significantly decreased. Treatment of HepG2 cells with either CsA or Nva2-Cs doubled the mitochondrial cytochrome oxidase and carnitine acetyl-transferase, as well as microsomal NADPH-cytochrome c reductase activities. Such treatment also increased the cyanide-insensitive beta-oxidation of fatty acids in peroxisomes, as well as cytoplasmic DT-diaphorase and glutathione transferase activities. Prolonged treatment of the cells with CsA did not result in any cumulative effect. HepG2 cells appear to be suitable for studying the effects of cyclosporins on cellular structure and metabolism and in this system the two drugs studied here exhibited similar effects.
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PMID:Modulation of metabolism in HepG2 cells upon treatment with cyclosporin A and Nva2-cyclosporin. 164 68


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