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 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 method of purification up to homogenous states and properties of NADP-reductase of purple bacteria Thiocapsa roseopersicina, strain BBS, are described. The molecular weight of NADP-reductase is about 47 000; it is flavoprotein consisting of two subunits. Atebrim and chloromercury bensoate inhibit the activity of NADP-reductase (34% and 33--60%, respectively). The enzyme is specific to NADPH; it catalyzes menadion-reductase reaction, diaphorase reaction of benzyl viologen reduction, oxidation of reduced benzyl viologen in the presence of NADP, reduction of ferredoxin and cytochrome c in the presence of NADPH, but it is not capable to catalyze transhydrogenase reaction.
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PMID:[Purification and properties of NADP-reductase of phototropic bacteria Thiocapsa roseopersicina]. 2 Jan 66

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

A flow diagram for the automated determination of ferricyanide reductase activity in red blood cells was prepared in the modules from AutoAnalyzer AA I (Technicon Instruments Inc). Ferricyanide reductase assay can be substituted for assay of cytochrome b5 reductase (EC 1.6.2.2), which plays a major role in reducing methaemoglobin in erythrocytes, and is defective specifically in the erythrocytes of patients with hereditary methaemoglobinaemia. The effective sampling rate of the analysis is 30/h, and less than 0.05 ml of whole blood is required. Interference of haemoglobin with absorption by potassium ferricyanide at 420 nm is effectively exculded by dialysis. This automated method was compared with the accepted diaphorase method, and it distinguished clearly the ferricyanide reductase activity of cord bloods from that of adult bloods. The activity of the blood from a patient with hereditary methaemoglobinaemia was only residual. It is suggested that the method is useful as a mass screening test for hereditary methaemoglobinaemia.
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PMID:Automated determination of red cell methaemoglobin reductase activity by a continuous-flow system for screening hereditary methaemoglobinaemia. 46 15

The organic phosphate allosteric effectors of hemoglobin, inositol hexaphosphate, 2,3-diphosphoglycerate, and ATP, interact with NADH-methemoglobin reductase (NADH-diaphorase). Significant inhibitory effects on the enzyme were found when dichlorophenolindophenol, or ferricyanide were used as electron acceptors in place of methemoglobin. In contrast, apparent stimulation of enzyme activity was observed when adult human methemoglobin was used as the electroganic phosphate on the rate of reaction due to its interaction with the substrate methemoglobin to produce the favored T type of quaternary conformation. The inhibitory effect of inositol hexaphosphate on the enzyme is associated with a perturbation in the reactivity of essential sulfhydryl group(s) on the enzyme. It is suggested that the interaction of the organic phosphate with the enzyme as well as with the substrate is significant in determining the overall rate of methemoglobin reduction.
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PMID:Inhibition of NADH-methemoglobin reductase by organic phosphates. 49 34

Histochemical and biochemical studies on the folate metabolism (folic acid an its principal enzyme-dihydrofolate-reductase) in bovine cortex - gyrus marginallis in the process of ageing were performed, in parallel with NADH2-cytocrom-C-reductase (diaphorase). Folic acid and folate enzyme, weak positive in neurons in young age, increased in old age in nerve cells and especially in their processes and in capillaries. The diaphorase strongly increased in all cells, glia and vessels, in old age.
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PMID:Histochemical study on the dihydrofolatereductase and folic acid in mammalian brain cortex. 54 85

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

Rhodospirillum rubrum cell extracts have active NADP-reductase capable of catalyzing the diaphorase reaction in the presence of methyl viologene or benzyl viologene and NADPH-generating system. The greater part of NADP-reductase is localized in the soluble fraction of destroyed cells (90-10(3) g; 90 min). The purified preparation of NADP-reductase was found to contain 6 proteins, 4-5 of them possessing diaphorase activity. Partially purified NADP-reductase preparation with a period of half-inactivation of about two days has a molecular weight of 95 000 and absorption spectrum, characterized by two maxima at 410 and 430 nm. NADP-reductase preparation possesses also menadione-reductase activity, but showed no ability for transhydrogenase reaction and reduction of cytochrome c.
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PMID:[Purification and properties of Rhodospirillum rubrum NADP-reductase]. 81 42

The fungicide dexon (p-dimethylaminobenzenediazosulfonate, Na-salt) inhibits the NADH oxidase activity of submitochondrial particles (ETP) from beef heart (semi-inhibition concentration 1.4 muM), while the succinate oxidase activity is unaffected. Measurements of the activity of several enzymatic partial reactions of the respiratory chain of ETP suggest that dexon acts directly on the flavine of NADH dehydrogenase. Soluble NADH-cytochrome c-oxidoreductase (MAHLER) and rotenone-insensitive NADH ubiquinone reductase are also inhibited by dexon. At low concentrations of dexon, inhibition of ETP starts slowly only after addition of NADH. Preincubation without NADH increases the amount of inhibition, but does not prevent the time delay. It is assumed that an electron flux through the respiratory chain, or reduction of flavine is prerequisite for the reaction of dexon with the action site. Furthermore, dexon inhibits the NADH dehydrogenase located at the outer surface of the inner membrane of plant mitochondria, accessible to extramitochondrial NADH and insensitive to rotenone, as has been shown on isolated mitochondria from cauliflower (Brassica oleracea L). In addition, dexon inhibits selectively the NADH dehydrogenase of the DT diaphorase (ERNSTER) from rat liver cytosol. In contrast, the dicoumarol-insensitive NADH dehydrogenase (ZINSMEYER et al.) from rat liver cytosol, the NADH-cytochrome b5-reductase (STRITTMATTER) from rat liver microsomes, the rotenone-insensitive NADH-cytochrome c-oxidoreductase of the outer membrane of rat liver mitochondria, soluble NADH-oxidase from Escherichia coli, and NADH-dehydrogenase from human erythrocytes are not inhibited. The results suggest that dexon is a group reagent to certain pyridine nucleotide-dependent flavine enzymes.
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PMID:[Action of the systemic fungicide dexon on several NADH dehydrogenases]. 82 48

A sporadic case of central core disease in a 5 1/2-year-old girl is reported. Clinically, a retarded motor development existed, furthermore, a muscle weakness and hypotonia of the extremities and trunk, contractures of the hip- and knee-joint,and luxation of both hip-joints. Biopsy specimens are taken from both Mm. gastrocnemii. Muscle fibres show, by morphologic examination, 95 per cent cores, which are characteristic for this myopathy. A further abnormality is seen inthe histochemical preparations for phosphorylase, succinate dehydrogenase, NAD diaphorase tetrazolium reductase, myofibrillar ATPase as well as AS-reaction with and without diastase digestion. With these techniques the muscle fibres show an uniform reaction pattern in which the activities of the oxidative andglycolytic enzymes correspond to the type I fibres of healthy persons. The cores show a lack of a activity of the oxidative and glycolytic enzymes as well as are ATPase- and PAS-negative. By reason of this histochemical behaviour it is suggested that the cores are predominantly unstructured. The cause of this disease might be complex disturbances in the neuro-muscular system manifested in the fetal period.
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PMID:[A case of central core disease. Light microscopic and histochemical studies (author's transl)]. 84 74


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