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:1.6.99.3 (diaphorase)
5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The NADH: (acceptor) oxidoreductase (EC 1.6.99.3) was isolated from human erythrocyte ghosts by a procedure including Triton X-100 solubilization, affinity chromatography on an NAD+-Sepharose 4B column, ammonium sulfate precipitation, and isoelectric focusing. This enzyme preparation was characterized by a single band on the urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by a single precipitin line with its corresponding antiserum on double diffusion and immunoelectrophoresis. A 103-fold purification indicates that the oxidoreductase represents approximately 1% of the ghost protein mass. The specific activity of the purified enzyme was 112 units/mg protein. The pH optimum was 6.8 and the isoelectric point, pI, was 6.6 The oxidoreductase has a specificity for NADH as a cofactor. The NADPH was ineffective as a reducing agent. The enzyme activity was strongly temperature-dependent, displaying maximal activity between 35 and 40 degrees C. The energy of activation was 4.9 kcal. The enzyme activity was inhibited by sulfhydryl reagents, anionic detergents, and divalent ions. The amino acid composition of the purified enzyme is characterized by the presence of all common amino acids including half-cystine and tryptophan. The results of carbohydrate and lipid analyses indicated that the oxidoreductase is a glycolipoprotein with fucose, galactose, mannose, and glucosamine as the sugar components and cholesterol and sphingomyelin as the lipid constituents. The apparent subunit molecular weight estimated by urea-sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence and presence of 2-mercaptoethanol was 40,000. The antiserum completely inhibited the enzymic activity at the equivalence point. We suggest that the membrane-bound NADH: (acceptor) oxidoreductase might be a transmembrane protein.
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PMID:Isolation and partial characterization of human erythrocyte membrane NADH: (acceptor) oxidoreductase. 3 37

1. Both NADH and NADPH supported the oxidation of adrenaline to adrenochrome in bovine heart submitochondrial particles. The reaction was completely inhibited in the presence of superoxide dismutase, suggesting that superoxide anions (O(2) (-)) are responsible for the oxidation. The optimal pH of the reaction with NADPH was at pH7.5, whereas that with NADH was at pH9.0. The reaction was inhibited by treatment of the preparation with p-hydroxymercuribenzoate and stimulated by treatment with rotenone. Antimycin A and cyanide stimulated the reaction to the same extent as rotenone. The NADPH-dependent reaction was inhibited by inorganic salts at high concentrations, whereas the NADH-dependent reaction was stimulated. 2. Production of O(2) (-) by NADH-ubiquinone reductase preparation (Complex I) with NADH or NADPH as an electron donor was assayed by measuring the formation of adrenochrome or the reduction of acetylated cytochrome c which does not react with the respiratory-chain components. p-Hydroxymercuribenzoate inhibited the reaction and rotenone stimulated the reaction. The effects of pH and inorganic salts at high concentrations on the NADH- and NADPH-dependent reactions of Complex I were essentially similar to those on the reactions of submitochondrial particles. 3. These findings suggest that a region between a mercurialsensitive site and the rotenone-sensitive site of the respiratory-chain NADH dehydrogenase is largely responsible for the NADH- and NADPH-dependent O(2) (-) production by the mitochondrial inner membranes.
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PMID:NADH- and NADPH-dependent formation of superoxide anions by bovine heart submitochondrial particles and NADH-ubiquinone reductase preparation. 3 43

The action of two radioprotectors--cysteamine and cystamine--on the liver microsomal multi-enzyme hydroxylating system, a key stem in drug and biological compounds metabolism, has been studied. Their effects have been systematically analysed at the level of individual enzyme activities and global functions. The two compounds are quite inactive on NADPH and NADH cytochrome c reductase activities, but slightly denature the cytochrome P450 into cytochrome P420. Furthermore, they do inhibit to some extent (30 per cent at 10(-2) M) the rate of codeine hydroxylation and totally suppress ((at 10(-2) M) the NADPH-induced lipid peroxidation which occurs during enzymatic functioning. These results are discussed in the light of the toxicity of radioprotectors.
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PMID:Biochemical effects on radioprotective agents on the liver microsomal hydroxylating system: in vitro studies. 9 66

The effects of cortisol on components of the liver microsomal mixed function oxidase system (MFO) of immature and starved rainbow trout, Salmo gairdnerii, Rich., were studied 3, 7 and 21 days after intraperitoneal implantation of cortisol-containing cholesterol pellets. The treatment resulted in significantly elevated NADPH cytochrome c reductase activities, concomitant with elevated plasma cortisol levels, at all sampling events, while no significant effects on either liver cytochrome P-450 or microsomal protein contents was observed. The cortisol-treated fish lost considerably more body weight than corresponding controls during the experimental period, while the effects on liver wet weight and liver somatic index were inconclusive.
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PMID:Effects of cortisol administration on components of the hepatic microsomal mixed function oxidase system (MFO) of immature rainbow trout (Salmo gairdnerii Rich.). 10 Oct 22

Candida tropicalis synthesizes a hydroxylase (3 to 5 nmol of product formed per minute per milligram of protein) and a cytochrome P-450 (0.10 to 0.13 nmol per milligram of protein) during growth on n-tetradecane. A three- to four-fold increase in the level of NADPH cytochrome c reductase is also observed in those cells as compared to the level of cells grown on glycerol. The most efficient inducers of the hydroxylase and of cytochrome P-450 are straight-chain alkanes having at least 10 carbon atoms. Alkenes and higher alcohols are also good inducers. There is little or no growth on ramified hydrocarbons such as pristane and on long-chain aldehydes and fatty acids. The partial inhibition of growth on decane is probably due to the denaturation of the microsomal electron carrier systems by the fatty acid formed by hydroxylation of the decane in the yeast.
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PMID:Hydroxylase regulation in Candida tropicalis grown on alkanes. 10 10

p-Aminophenol administration lowered the microsomal cytochrome P-450 and b5 content and decreased the activity of NADPH cytochrome c reductase in kidney, but not in liver. Kidney GSH was depleted to 29% of the control value at 2 h, and only partly restored (50% of control) at 24 h. Liver GSH was transiently decreased, the lowest levels (77% of control) occurring at 30 min. The maximum level of covalently bound radioactivity was at two hours when 16.8% of the total radioactivity in kidney, 1.5% in liver and 3.6% in plasma was protein bound. At this time 81% of the total radioactivity in kidney and 95% of that in the liver was present in the soluble fraction.
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PMID:The nephrotoxicity of p-aminophenol. I. The effect on microsomal cytochromes, glutathione and covalent binding in kidney and liver. 11 95

The influence of the mode of preparation upon some of the characteristics of white adipose tissue plasma membranes and microsomes has been reported. Plasma membrane fractions prepared from mitochondrial pellet were shown to have higher specific activities of (Mg2+ + Na+ + K+)-ATPase than plasma membranes originating in crude microsomes. Isolation of fat cells by collagenase treatment was found to result in a decrease in specific activity of the plasma membrane enzymes; in plasma membranes prepared from isolated fat cells, the specific activity values obtained for (Mg2+ + Na+ +k+)-ATPase and 5'-nucleotidase were only 42% and 6.3% respectively of those obtained in plasma membranes prepared from whole adipose tissue. Purification of whole adipose tissue crude microsomes by hypotonic treatment caused extensive solubilization of the endoplasmic reticulum marker enzymes, NADH oxidase and NADPH cytochrome c reductase. The lability of endoplasmic reticulum marker enzymes, however, was found to be greatly diminished in the preparations from isolated fat cells. The possibility that NADH oxidase and NADPH cytochrome c reductase activities found in the plasma membranes are microsomal enzymes adsorbed by the plasma membranes is discussed. The peptide patterns as well as the NADH oxidase and NADPH cytochrome c reductase activity patterns of plasma membranes and purified microsomes were compared by means of sodium dodecyl sulfate or Triton X-100 polyacrylamide gel electrophoresis.
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PMID:Comparison of plasma membranes and endoplasmic reticulum fractions obtained from whole white adipose tissue and isolated adipocytes. 12 89

Incubation of rat cytochrome b5 (D-b5) with rat liver microsomes resulted in specific binding of the hemoprotein. The bound hemoprotein was rapidly reduced by NADH. The NADH cytochrome c reductase activity in these preparations increased in proportion to the amount of cytochrome. In contrast to D-b5, which inhibited N-demethylation and the NADH synergism, the binding of cytochrome b5 preparations, reconstituted from heme and apocytochrome b5 had no effect on either the NADPH-dependent N-demethylation of aminopyrine or ethylmorphine or the NADH synergism observed with rat liver microsomes. In addition, manganese protoporphyrin-apocytochrome complex, when bound to microsomes in amounts equilvalent to D-b5, showed no effect on N-demethylation activity. These results suggest that homogeneous cytochrome b5 contains contaminating amounts of tightly bound detergent which presumably is removed during the extraction of the heme from the apocytochrome.
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PMID:The role of cytochrome b5 in mixed function oxidations: effect of microsomal binding of the hemoprotein on hepatic N-demethylations. 16 51

An improved procedure for the preparation of cobalt-cytochrome c has been developed. Various factors influencing the cobalt insertion process are discussed. The optical spectra of cobalt-cytochrome c suggest a six-coordinated species. The spectral shifts occurring with oxidation-reduction are compared with those observed for deoxy-cobaltohemoglobin and ferrocytochrome c and attributed to the effect of d(z2) electron on stereoelectronic interactions between the axial ligands and the porphyrin pi systems. Cobalt-cytochrome c has Em,7 = -140 +/- 20 mV as compared to an Em,7 of +250mV for ferrocytochrome c. An explanation for this negative Em,7 is offered. Cobaltocytochrome c is oxidized by cytochrome oxidase at about 45% of the rate for native cytochrome c. On the other hand cobalticytochrome c was not reduced by microsomal NADH or NADPH cytochrome c reductase nor by mitochondrial NADH or succinate cytochrome c reductase. It appears that the integrity of the reductase binding site is destroyed and the oxidase binding site has been modified by cobalt substitution.
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PMID:Cobalt-cytochrome c. I. Preparation, properties, and enzymic activity. 16 80

Enzyme preparations were exposed to microwave radiation at 2450 MHz and enzymatic activity was simultaneously monitored spectrophotometrically with a crossed-beam exposure detection system. Enzymes studied were glucose 6-phosphate dehydrogenase from human red blood cells and yeast, adenylate kinase from rat liver mitochondria and rabbit muscle, and rat liver microsomal NADPH cytochrome c reductase. No difference was found between the specific activity at 25 degrees C of unirradiated controls and enzyme preparations irradiated at an absorbed dose rate of 42 W/kg.
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PMID:Measure of enzymatic activity coincident with 2450 MHz microwave exposure. 17 63


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