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)

In the presence of Fe-3+ and complexing anions, the peroxidation of unsaturated liver microsomal lipid in both intact microsomes and in a model system containing extracted microsomal lipid can be promoted by either NADPH and NADPH : cytochrome c reductase or by xanthine and xanthine oxidase. Erythrocuprein effectively inhibits the activity promoted by xanthine and xanthine oxidase but produces much less inhibition of NADPH-dependent peroxidation. The singlet-oxygen trapping agent, 1, 3-diphenylisobenzofuran, had no effect on NADPH-dependent peroxidation but strongly inhibited the peroxidation promoted by xanthine and xanthine oxidase. NADPH-dependent lipid peroxidation was also shown to be unaffected by hydroxyl radical scavengers.. The addition of catalase had no effect on NADPH-dependent lipid peroxidation, but it significantly increased the rate of malondialdehyde formation in the reaction promoted by xanthine and xanthine oxidase. The results demonstrate that NADPH-dependent lipid peroxidation is promoted by a reaction mechanism which does not involve either superoxide, singlet oxygen, HOOH, or the hydroxyl radical. It is concluded that NADPH-dependent lipid peroxidation is initiated by the reduction of Fe-3+ followed by the decomposition of hydroperoxides to generate alkoxyl radicals. The initiation reaction may involve some form of the perferryl ion or other metal ion species generated during oxidation of Fe-2+ by oxygen.
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PMID:The mechanism of liver microsomal lipid peroxidation. 23 6

A dihydrodipicolinate reductase containing flavin was purified from sporulating Bacillus subtilis PCI 219. The purified enzyme appeared homogeneous by dise gel electrophoresis. Its molecular weight was estimated as 74,000 by gel filtration on Sephadex G-200, and as 18,500 by electrophoresis on sodium dodecylsulfate polyacrylamid gel. These results suggest that the enzyme is composed of four subunits. The prosthetic group was identified as FMN, and one mole of the enzyme contained two moles of FMN. Both NADPH and NADH acted as coenzyme, though NADH was less effective. The enzyme also exhibited diaphorase activity. The pH optimum was 6.1. The enzyme was inhibited by dipicolinate but not by lysine or alpha, epsilon-diaminopimelate.
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PMID:A new flavin enzyme catalyzing the reduction of dihydrodipicolinate in sporulating Bacillus subtilis I. Purification and properties. 23 91

1. The effects of halothane (CF3CHBrCl), a volatile anaesthetic agent, on electron transfer in isolated rat liver microsomal preparations were examined. 2. At halothane concentrations achieved in tissues during clinical anaesthesia (1-2mM), halothane shifts the redox equilibrium of microsomal cytochrome b5 in the presence of NADPH towards the oxidized form. Halothane accelerates stoicheiometric consumption of NADPH and O2, increases the rate of reoxidation of NADH-reduced microsomal ferrocytochrom b5, but does not affect NADPH- or NADH-cytochrome c reductase activity. The enhanced microsomal electron flow seen in the presence of halothane is not diminished by CO nor is it increased by pretreatment of the animals with phenobarbital. 3. The effects of halothane are maximum in microsomal preparations isolated from animals fed on a high-carbohydrate diet to induce stearate desaturase activity. Changes in microsomal electron transfer caused by halothane are in all cases abolished by low concentrations (1-2mM) of cyanide. Microsomal stearate desaturase activity is unaffected by halothane. 4. The first-order rate constant for oxidation of membrane-bound ferrocytochrome b5 in the absence of added substrate (k1 equals 1.5 times 10(-3)A-1) is similar to that for autoxidation of purified ferrocytochrome b5(k1 equals 7 times 10(-3)S-1) the rate of autoxidation of soluble ferrocytochrome b5 is unaffected by halothane. 5. It is concluded that the effects of halothane on microsomal electron transfer are not related to cytochrome P-450 linked metabolism but rather arise from the interaction of halothane with the cyanide-sensitive factor of the stearate desaturase pathway.
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PMID:The effects of halothane on hepatic microsomal electron transfer. 23 6

NADH- and NADPH-diaphorases, 3alpha-, delta5-3beta-, 11beta- and 17beta-hydroxy-steroid dehydrogenases (HSD) and lipids were studied histochemically in the testes and adrenals of male bank voles kept in a long (16L:8D) or a short (8L:16D) photoperiod (Groups L and S, respectively). At 67 days of age the Group L males were heavier and had active and significantly larger testes than Group S males. The testes of Group S males were regressed and were also significantly smaller than those of 18-day-old animals born and reared in a 18L:6D photoperiod. Lipid droplets were detected in the Leydig cells and intratubular spaces in the testes of Group L animals, but were absent from those of Group S voles. The adrenal cortex of the Group L animals was virtually devoid of lipids, but large lipid inclusions were present in the basal zona fasciculata of the Group S voles. In the Group L testes the diaphorase activities were more intense and the difference in enzymic activity between the seminiferous epithelium and the Leydig cells was more pronounced (especially for NADH-diaphorase) than that in the testes of Group S animals. Moreover, the 3alpha-- and delta5-3beta-HSD activities were much stronger in the testes of sexually active animals; 17beta-HSD activity was present in the Leydig cells of the active testes, and absent in the regressed testes. There was no marked difference between the two groups of animals with regard to the distribution or intensity of diaphorases, 3alpha-, delta5-3beta-, 11beta- or 17beta-HSD in the adrenal cortex. It is concluded that a decline in steroid synthesis occurs in the testes of voles kept in a short photoperiod. The large lipid inclusions observed in the adrenal cortex of such animals suggest decreased corticosteroid synthesis and/or secretion.
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PMID:A histochemical study on the effects of photoperiod on gonadal and adrenal function in the male bank vole (Clethrionomys glareolus). 36 52

Cell-free extracts of a streptomycin-bleached strain of Euglena gracilis var. bacillaris have been examined for enzyme systems primarily responsible for the oxidation of reduced pyridine nucelotides. NADH lipoyl dehydrogenase, NADH and NADPH oxidase, NADH and NADPH diaphorase, and NADH and NADPH cytochrome c reductase have been demonstrated. The NADPH-linked enzymes had lower activity rates and were less sensitive to N-ethyl maleimide and p-hydroxymercuribenzoate than their NADH-linked counterparts. NADH cytochrome c reductase was the most sensitive to antimycin A. Michaelis-Menten constants (Km) determined were as follows: NADH diaphorase, 350 muM; NADPH oxidase 150 muM ; NADH lipoyl dehydrogenase, 0.35 muM. Enzyme activities after storage at -5 C indicate that the diaphorases are less labile than the other tested enzymes, and the differential activities of the NADH and NADPH linked enzymes suggest that functionally they may have different roles.
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PMID:Reduced pyridine nucleotide oxidases of Eugena gracilis var. bacillaris. 40 56

Sprague-Dawley rats were fed a synthetic diet deficient in or containing thiamin (20 mcg/gm food), riboflavin (50 mcg/gm), or pyridoxine (50 mcg/gm) while receiving either norethindrone (1.0 or 10.0 mg/rat/day) or methocel solution to determine the influence of this oral contraceptive on drug-metabolizing enzymes of female rat liver. Ingestion of high levels of thiamin significantly decreased the activity of cytochrome P-450, NADPH cytochrome c reductase, and the metabolism of aniline and ethylmorphine. Diets containing riboflavin significantly depressed V max for aniline hydroxylation and ethylmorphine demethylation while NADPH cytochrome c reductase was elevated. V max for aniline hydroxylase was the only drug-metabolizing enzyme which was affected by high levels of dietary pyridoxine. Norethindrone slightly depressed or left unaffected the activity of cytochrome P-450 regardless of diet. Norethindrone increased activity of c reductase and ethylmorphine N-demethylase or left it unchanged. Norethindrone induces aniline hydroxylase in all diets except those deficient in thiamin and riboflavin. The effects of norethindrone on the kinetics of aniline metabolism were unexplained by substrate enzyme-binding kinetics. However, it is apparent that dietary status affects the parameters studied and the effects of norethindrone.
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PMID:Influence of norethindrone on drug-metabolizing enzymes of female rat liver in various B-vitamin deficiency states. 40 27

The effect of thiamin deficiency on the metabolism of the oral contraceptive mestranol by female rat liver enzymes was determined. Rats were fed a diet for 3 weeks containing 0, .3, .7, 2.0, or 20 mcg thiamin/gm food before decapitation and extraction of liver microsomes. Mestranol was incubated with 1 ml microsomes from 250 mg liver and the metabolic reaction started by addition of cofactors and NADPH. Liver microsomes from rats fed a thiamin-deficient diet had 3 times the capacity to metabolize mestranol as microsomes from rats fed a thiamin-rich diet. The incremental addition of thiamin to the diet depressed mestranol 0-demethylation, NADPH cytochrome c reductase, and cytochrome P-450 content. Pair-feeding experiments indicate that the carbohydrate portion of the food is responsible for decrease in cytochrome c, while thiamin levels are responsible for changes in the other 2.
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PMID:The influence of thiamin deficiency on the metabolism of the oral contraceptive mestranol [3-methoxy-17-ethynyl-1,3,5(10)-estratrien-17 beta-o1] by female rat liver enzymes. 41 82

SVA was used to separate liver cells from rats pretreated for 3 days with PB (40 mg/kg intraperitoneally, twice daily) or 3-MC (50 MG/KG AS A SINGLE INJECTIOn). Twelve fractions of cells were collected with s's ranging from 97 mm/hr (fraction1) to 25 mm/hr (fraction 12). Cells in each fraction were sized and counted electronically. PB caused the average volume of the largest cells recovered (fraction 1) to increase to 16, 725 micrometer3 from 10,500 micrometer3 previously reported in untreated animals. The number of cells recovered in the fast-sedimenting fractions (1 to 6) also increased, but there was only a small rise in the average model volume of hepatocytes determined prior to SVA. In cell suspensions analyzed after PB treatment no evidence was found for a discontinuity in the distribution of density-volume characteristics as previously described in hepatocytes from untreated rats. As expected, prior to sedimentation analysis, hepatocyte suspensions from rats treated with PB contained increased cytochrome P-450. The average ratio (n = 4) of P-450 in separated to unseparated cells ranged from 2.75 (fractions 1 + 2) to 0.38 (fractions 11 + 12), giving a 6.8-fold range in quantity of cytochrome per cell. Over this range, cell volume increased 4.2-fold, indicating a gradient in P-450 concentration similar to that previously reported to exist in cells from untreated rat liver. The gradient for AHH activity was 6.7-fold, suggesting that activity of MFO's paralleled the increase in cytochrome concentration. 3-MC pretreatment caused no significant increase in either size or number of cells in the fast-sedimenting fractions, but the discontinuity in density-volume characteristics which distinguished fast and slow sedimenting cells of untreated rats became marked. Furthermore, both the size and number of cells recovered in fractions 7 to 11 (which include the modal peal volume of unseparated hepatocytes) were increased. The gradient of P-450 (OR P1-450) was less steep in 3-MC-treated cells with pooled fractions 1 and 2 containing an average of 4.62 times as much cytochrome as fractions 11 and 12. The gradient for AHH was 4.29 times. The range of cell volume was 3.3-fold over this range. Additional experimental work was performed to determine whether P-450, AHH, or NADPH cytochrome c reductase exhibited differences in activity or concentration per unit of cell volume between cells on either side of fraction 7 where discontinuity had been noted. Each variable was expressed per unit of cell volume in fractions 5 and 9; ratios were compared but were indistinguishable from unity. It was concluded that induction of MFO activity had occurred equally in both populations of cells. Densities were calculated from s and cell volume. Noticeable loss of density followed PB treatment in cells of all sizes. 3-MC had less of an effect on density but enhanced the increment in density observed at fraction 7, which corresponds to the division between cells with distinct sedimentation characteristics...
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PMID:Effects of phenobarbital and 3-methylcholanthrene pretreatment on size, sedimentation velocity, and mixed function oxygenase activity of rat hepatocytes. 41

Elaidic and linoleic acids were administered at doses of 40 and 200 mg/kg i.p. every second day for 4 weeks to rats fed a fat-free diet. The fatty acids had only a slight effect on the weight gain of the animals. The amount of microsomal protein was slightly decreased with the higher dose of linoleic acid. The higher dose level of both fatty acids decreased the microsomal phospholipid content. The relative amounts of microsomal phospholipid fatty acids were also altered due to fatty acid administration. The activity of microsomal NADPH cytochrome c reductase and microsomal cytochrome P-450 contents were decreased by the higher dose of linoleic acid. The hepatic aryl hydrocarbon hydroxylase and p-nitroanisole O-demethylase activities decreased in fatty acid-treated rats. The UDP-glucuronosyltransferase activity was also lowered after the fatty acid administration. The results suggest that fatty acid-induced changes in the activities of drug-metabolizing enzymes may be due to the microenvironmental changes of membrane-bound enzymes.
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PMID:Regulation of hepatic drug metabolism by elaidic and linoleic acids in rats. 41 54

Thiourea and diethylthiourea, two compounds which react with hydroxyl radicals, inhibited NADPH-dependent microsomal oxidation of ethanol and 1-butanol. Inhibition by both compounds was more effective in the presence of the catalase inhibitor, azide. Inhibition by thiourea was noncompetitive with respect to ethanol in the absence of azide but was competitive in the presence of azide. Urea, a compound which does not react with hydroxyl radicals or H2O2, was without effect. Thiourea had no effect on NADH- and NADH-cytochrome c reductase, NADPH oxidase, and NADH- and NADPH-dependent oxygen uptake. Thiourea inhibited the activities of aniline hydroxylase and aminopyrine demethylase. Thiourea, but no other hydroxyl radical scavengers, e.g., dimethyl sulfoxide, mannitol, and benzoate, reacted directly with H202 and decreased H2O2 accumulation in the presence of azide. Therefore the actions of thiourea are complex because it can react with both hydroxyl radicals and H2O2. Differences between the actions of thiourea and those previously reported for dimethyl sulfoxide, mannitol, and benzoate, e.g., effects on drug metabolism, effectiveness of inhibition in the absence of azide, or kinetics of the inhibition, probably reflect the fact that thiourea reacts directly with H2O2 whereas the other agents do not. The current results remain consistent with the concept that microsomal oxidation of alcohols involves interactions of the alcohols with hydroxyl radicals generated from microsomal electron transfer.
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PMID:Effect of thiourea on microsomal oxidation of alcohols and associated microsomal functions. 42 8


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