Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.6 (NADPH oxidase)
 10,295 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The soluble NADH dehydrogenase of low molecular weight, isolated from complex I (NADH:ubiquinone oxidoreductase, EC 1.6.5.3) of the respiratory chain, has been shown to have NADPH dehydrogenase and NADPH leads to NAD transhydrogenase activities. Both activities are greatly increased in the presence of added guanidine-HCl and at pH values less than 6.5. The chromophores of the soluble enzyme (flavin and iron--sulfur centers) are reduced by NADH and NADPH to the same extent. The latter reduction is extremely slow, and is considerably stimulated in the presence of guanidine-HCl. The soluble dehydrogenase has little or no NADH leads to NADP and NADPH leads to NADP transhydrogenase activity. The former reaction is known to be energy-linked in submitochondrial particles; the latter was shown in the present studies also to be energy-linked. In view of the above and earlier results, possible mechanisms for dehydrogenation and transhydrogenation (nonenergy-linked and energy-linked) involving reduced and oxidized NAD and NADP are proposed.
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PMID:Dehydrogenase and transhydrogenase properties of the soluble NADH dehydrogenase of bovine heart mitochondria. 1 55

1. Oxidation of NADPH by various acceptors catalyzed by submitochondrial particles and a partially purified NADH dehydrogenase from beef heart was investigated. Submitochondrial particles devoid of nicotinamide nucleotide transhydrogenase activity catalyze an oxidation of NADPH by oxygen. The partially purified NADH dehydrogenase prepared from these particles catalyzes an oxidation of NADPH by acetylpyridine-NAD. In both cases the rates of oxidation are about two orders of magnitude lower than those obtained with NADH as electron donor. 2. The kinetic characteristics of the NADPH oxidase reaction and reduction of acetylpyridine-NAD by NADPH are similar with regard to pH dependences and affinities for NADPH, indicating that both reactions involve the same binding site for NADPH. The binding of NADPH to this site appears to be rate limiting for the overall reactions. 3. At redox equilibrium NADPH and NADH reduce FMN and iron-sulphur center 1 of NADH dehydrogenase to the same extents. The rate of reduction of FMN by NADPH is at least two orders of magnitude lower than with NADH. 4. It is concluded that NADPH is a substrate of NADH dehydrogenase and that the nicotinamide nucleotide is oxidized by submitochondrial particles via the NADH--binding site of the enzyme.
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PMID:The mechanism of oxidation of reduced nicotinamide dinucleotide phosphate by submitochondrial particles from beef heart. 2 68

The actions of Dexon on the NADH-ferricyanide oxidoreductase and the NADPH oxidase system of electron transfer particles (ETP) from beef heart as well as on the NADPH-cytochrome c oxidoreductase from brewer's yeast (Saccharomyces carlsbergensis Hansen) were investigated. The inhibition of the NADH dehydrogenase activity of ETP and that of the yeast enzyme correspond with respect to the following characteristics: 1) increase in the inhibition, 2) enhancement of the Dexon sensitivity by one order of magnitude after preincubation in the presence of NAD(P)H, 3) irreversibility of the inhibition, 4) no detectable changes in the spectral properties and in coenzyme activity of FMN after acid extraction from Dexon-treated enzyme. The inhibition of the NADH dehydrogenase activity of ETP is diminished by both NAD+ and FMN. However, no interaction of Dexon with NAD(P)H or FMN could be detected in the absence of enzyme or apoenzyme. The concentration of half-inhibition by Dexon for the yeast enzyme corresponds with its FMN concentration. It is proposed that both apoenzyme, NAD(P)H and FMN are involved in the interaction with Dexon. Possible mechanisms of binding are both complanar complexations of the ring systems and a triazene formation between FMNH2 and Dexon. The NADPH oxidase activity of the ETP is partly inhibited; the share inhibited by Dexon may represent the pathway via the transhydrogenase reaction.
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PMID:[Mechanism of action of the inhibition of pyridine-nucleotide-dependent flavine enzymes using the systemic fungicide Dexon]. 41 38

Monodehydroascorbate reductase (EC 1.6.5.4) was purified from cucumber fruit to a homogeneous state as judged by polyacrylamide gel electrophoresis. The cucumber monodehydroascorbate reductase was a monomer with a molecular weight of 47,000. It contained 1 mol of FAD/mol of enzyme which was reduced by NAD(P)H and reoxidized by monodehydroascorbate. The enzyme had an exposed thiol group whose blockage with thiol reagents inhibited the electron transfer from NAD(P)H to the enzyme FAD. Both NADH and NADPH served as electron donors with Km values of 4.6 and 23 microM, respectively, and Vmax of 200 mol of NADH and 150 mol of NADPH oxidized mol of enzyme-1 s-1. The Km for monodehydroascorbate was 1.4 microM. The amino acid composition of the enzyme is presented. In addition to monodehydroascorbate, the enzyme catalyzed the reduction of ferricyanide and 2,6-dichloroindophenol but showed little reactivity with calf liver cytochrome b5 and horse heart cytochrome c. The kinetic data suggested a ping-pong mechanism for the monodehydroascorbate reductase-catalyzed reaction. Cucumber monodehydroascorbate reductase occurs in soluble form and can be distinguished from NADPH dehydrogenase, NADH dehydrogenase, DT diaphorase, microsome-bound NADH-cytochrome b5 reductase, and NADPH-cytochrome c reductase by its molecular weight, amino acid composition, and specificity of electron acceptors and donors.
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PMID:Monodehydroascorbate reductase from cucumber is a flavin adenine dinucleotide enzyme. 405 27

1. Paraquat and diquat produce only a slight increase in the oxygen uptake of rat liver mitochondria, and it is likely that they do not penetrate the mitochondrial membrane. 2. In mitochondrial fragments inhibited by antimycin A or by Amytal, both substances stimulate oxygen uptake with NADH or beta-hydroxybutyrate as substrate but not with succinate. The NADH dehydrogenase of the respiratory chain appears to be involved, at a site only partially inhibited by Amytal. 3. An NADPH oxidase activity is stimulated in rat liver microsomes by diquat, and to a smaller extent by paraquat; diquat also causes an NADH oxidase activity to develop. The effect is not inhibited by carbon monoxide or p-chloromercuribenzoate, and it is probable that a flavoprotein is involved by a mechanism not requiring thiol groups. 4. One molecule of oxygen can oxidize two molecules of NADPH in the stimulated microsomal system, the hydrogen peroxide produced being broken down by a catalase activity in the microsomes. 5. Diquat can stimulate NADH oxidase and NADPH oxidase activity in the postmicrosomal soluble fraction; the enzyme involved may be DT-diaphorase. 6. The mechanism of these reactions and their significance in relation to the toxicity of the dipyridilium compounds are discussed.
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PMID:The action of paraquat and diquat on the respiration of liver cell fractions. 438 31

The effects of an oral neomycin and penicillin regimen on intestinal bacteriology and on morphology and function of the small intestine of mice were investigated. Quantitative and qualitative stool cultures on selective media of the treated animals revealed only growth of yeast organisms. The treated animals developed enlargement of the ceca with fluid contents and watery stools, resembling characteristics of germfree animals. Radioautography with tritiated thymidine revealed an increased epithelial cell migration rate in the mice treated with the antibiotics for 3 to 5 wk. A slight increase in villus height was also noted. The treated male mice showed greater variance than the treated females in epithelial cell migration rates. Histochemical staining reactions showed a decrease in nonspecific esterase and in NADH dehydrogenase activity in the proximal gut of the antibiotic animals. Stains of distal gut and those for acid and alkaline phosphatase, NADPH dehydrogenase, lactic dehydrogenase, and succinic dehydrogenase were similar to the controls. A slight increase in sucrase activity and a slight decrease in lactase activity in the antibiotic animals was observed in contrast to control animals. Germfree mice, however, had greater sucrase and lactase activity. Transport of L-methionine was slightly reduced in the distal segment of the treated animals. Since the direction of these changes is away from the intestinal state observed in germfree animals, they are probably the result of the direct action of the antibiotics on the gut.
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PMID:Effects of neomycin and penicillin administration on mucosal proliferation of the mouse small intestine. With morphological and functional correlations. 438 18

1. A spectroscopic resolution has been made of the components contributing to the ;iron-flavoprotein' trough extending from 450 to 520nm in the reduced-minus-oxidized difference spectrum of submitochondrial particles of Torulopsis utilis. 2. Seven components were identified other than cytochrome b, ubiquinone and succinate dehydrogenase. On the basis of the effects of iron- and sulphate-limited growth of cells on their subsequently derived electron-transport particles, and also by consideration of analytical measurements of the concentration of FMN, FAD, non-haem iron and acid-labile sulphide in the electron-transport particles in relation to the magnitude of the spectroscopic changes, it was possible to identify five of these components as follows: species 1a, the flavin of NADH dehydrogenase ferroflavoprotein; species 1b, the iron-sulphur component of NADH dehydrogenase ferroflavoprotein; species 1', the flavin of an NADPH dehydrogenase; species 2, an iron-sulphur or ferroflavoprotein component; species 3, the flavin of l-3-glycerophosphate dehydrogenase. Two additional components were a fluorescent flavoprotein, probably lipoamide dehydrogenase, and a b-type cytochrome reducible by NADH or NADPH but not reoxidizable by the respiratory chain. 3. Species 1b and 2 were undetectable in electron-transport particles from iron- or sulphate-limited cells, but could be recovered in vivo under non-growing conditions. 4. The recovery in vivo of species 2 but not species 1b was inhibited by cycloheximide. 5. The recovery of species 1b correlates with the recovery of site 1 conservation. 6. The recovery of species 1b with species 2 correlates with the recovery of piericidin A sensitivity. 7. Evidence is presented for an NADPH dehydrogenase distinct from NADH dehydrogenase. The oxidation of NADH and NADPH by the respiratory chain is sensitive to piericidin A, and an iron-sulphur protein common to both pathways (species 2) is suggested as the piericidin A-sensitive component. 8. The approximate E'(0) (pH7.0) values of species 1 (a and b, low potential) and species 2 (high potential) indicate that site 1 energy conservation occurs between the levels of species 1 (a and b) and species 2.
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PMID:Spectroscopic studies of flavoproteins and non-haem iron proteins of submitochondrial particles of Torulopsis utilis modified by iron- and sulphate-limited growth in continuous culture. 439 18

Cells of the aerotolerant anaerobe Giardia lamblia respire in the presence of oxygen. Endogenous respiration is stimulated by glucose but not by other carbohydrates and Krebs cycle intermediates. Endogenous and glucose-stimulated respiration are insensitive to cyanide, malonate, and 2,4-dinitrophenol, but are inhibited by atabrin and iodoacetamide. G. lamblia produces ethanol, acetate and CO2 both aerobically and anaerobically either from endogenous reserves or exogenous glucose. Molecular hydrogen is not produced. The following enzyme activities were detected in homogenates: hexokinase, fructose-biphosphate aldolase, pyruvate kinase, phosphoenolpyruvate carboxykinase, malate dehydrogenase, malate dehydrogenase (decarboxylating), pyruvate synthase, acetyl-CoA synthetase, alcohol dehydrogenase (NADP+), NADH dehydrogenase, NADPH dehydrogenase, NADPH oxidoreductase and superoxide dismutase. The enzymes of energy and carbohydrate metabolism are nonsedimentable (109 000 x g for 30 min). Activities of lactate dehydrogenase, hydrogenase, phosphate acetyltransferase, acetate kinase, citrate synthase, succinate dehydrogenase, fumarate hydratase and catalase were below the limits of detection. The results suggest the occurrence of glycolysis, energy production by substrate level phosphorylation and a flavin, iron-sulfur protein mediated electron transport system as well as the absence of cytochrome mediated oxidative phosphorylation and functional Krebs cycle.
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PMID:Energy metabolism of the anaerobic protozoon Giardia lamblia. 610 7

Quantitative cytochemical investigations have detected individual variations between murine peritoneal macrophages and have shown distinct difference between resident and exudate populations. The latter generally contain greater amounts of protein, RNA, acid phosphatase, succinate dehydrogenase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, and NADH dehydrogenase. On te other hand, no differences were detected in the cellular content of DNA, not-specific esterase, and NADPH dehydrogenase. In many instances they reflect the biochemical findings of other investigators including the stimulation of glycolysis, tricarboxylic acid cycle and hexose monophosphate shunt pathways, which can occur in elicited or activated macrophages. Although cytochemical differences between the two populations exist, it cannot be stated whether they represent distinct cell lines or different functional states of the same cell population.
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PMID:A quantitative cytochemical analysis of resident and exudate macrophages. 616 17

Iron-containing antigens present in membrane vesicles prepared from Escherichia coli ML 308-225 were analyzed by crossed immunoelectrophoresis following growth of the organism in the presence of 59Fe. Seven discrete antigens (or antigen complexes) are detected by autoradiography, and six contain primarily nonheme iron. Three immunoprecipitates are positively identified as NADH dehydrogenase (EC 1.6.99.3), NADPH dehydrogenase (EC 1.6.99.1), and glutamate dehydrogenase (EC 1.4.1.4) based on activity stains for these enzymes. Two other immunogens containing nonheme iron correspond to antigens no. 22 and 37 in the crossed immunoelectrophoresis reference pattern of Owen & Kaback [Owen, P., & Kaback, H. R. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 3148]. In addition, the immunoprecipitate corresponding to Braun's lipoprotein contains tightly bound iron.
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PMID:Resolution and identification of iron-containing antigens in membrane vesicles from Escherichia coli. 698 2


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