Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:EXPT02288 (NADH)
 21,914 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Large numbers of taste buds are distributed over the body surface of the channel catfish ictalurus punctatus, with the barbels having an especially high density. L-Alanine, as well as certain other amino acids, are taste stimuli in this animal. Epithelial tissue obtained by gentle scraping of the barbel surface was fractionated by differential centrifugation. A sedimentable fraction (P2) was prepared that was enriched in L[OH]alanine binding activity, the plasma membrane marker enzyme 5'-nucleotidase, and the mitochondrial marker succinate cytochrome c reductase, but not the microsomal marker NADH cytochrome c redu.ctase. Binding of L-[OH]alanine was measured using a Millipore filter method in which correction for non-specific binding was also determined. Time, temperature, and pH for measuring binding activity were established. At the optimal pH of 7.8, the KD for L-alanine is 4.8 X 10(-6) M. The first order dissociation rate constant at 6 degrees is 3.8 X 10(-4) s-1 and at 24 degrees it is 12.1 X 10(-4) s-1. The second order rate constant for association is between 10(2) and 10(3) M-1 S-1. Reversibility of the binding interaction was also demonstrates by the rapid displacement of bound L-[3H]alanine by a large excess of unlabeled L-alanine. That the binding does not represent incorporation into protein was confirmed by the lack of effect of puromycin. The amounts bound of several other chemostimulatory amino acids werealso determined.
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PMID:Biochemical studies of tast sensation. Binding of L-[3H]alanine to a sedimentable fraction from catfish barbel epithelium. 0 Apr 3

The activities of the cytochrome c reductases and of the D-T diaphorase in rat Leydig cell tumors have been described. The increase in enzymatic activity of the NADH cytochrome c reductase activity in functional tumors derived from interstitial cells of the rat testis is interpreted as being possibly related to hydroxylation of steroids by the neoplastic cells. Meanwhile, the increase in the activity of the D-T diaphorase in the other tumor is interpreted as being an anaplerotic reaction to substitute for the deficient shuttles for the transfer of reducing equivalents from the cytoplasm to the mitochondria observed in tumors.
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PMID:Dehydrogenation of reduced pyridine nucleotides by Leydig cell tumors of the rat testis. 0 36

A monooxygenase isolated from 5-day old etiolated Vinca rosea seedlings was shown to catalyze the hydroxylation of the monoterpene alcohols, geraniol and nerol, to their corresponding 10-hydroxy derivatives. Hydroxylase activity was inpendent upon NADPH (neither NADH nor combination of NADH, NADP+ and ATP served as substitutes) and O2. Geraniol hydroxylation was enhanced by dithiothreitol (monothiols were less effective) and inhibited by phospholipases, thiol reagents, metyrapone, and cytochrome c, as well as other inhibitors of cytochrome P-450 systems. Geraniol was hydroxylated at a faster rate than nerol, but the alcohols possessed similar apparent Km values. The membrane-bound hydroxylase was solubilized by treatment with sodium cholate, Renex-30, or Lubrol-WX. Cholate-treated enzyme was resolved by DEAE-cellulose chromatography and reconstitution of the hydroxylase was effected utilizing different fractions containing cytochrome P-450, a NADPH-cytochrome c reductase, and lipid.
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PMID:Characterization of a cytochrome P-450 dependent monoterpene hydroxylase from the higher plant Vinca rosea. 0 9

1. Formate inhibits cytochrome c oxidase activity both in intact mitochondria and submitochondrial particles, and in isolated cytochrome aa3. The inhibition increases with decreasing pH, indicating that HCOOH may be the inhibitory species. 2. Formate induces a blue shift in the absorption spectrum of oxidized cytochrome aa3 (a3 + a33+) and in the half-reduced species (a2 + a33+). Comparison with cyanide-induced spectral shifts, towards the red, indicates that formate and cyanide have opposite effects on the aa3 spectrum, both in the fully oxidized and the half-reduced states. The formate spectra provide a new method of obtaining the difference spectrum of a32+ minus a33+, free of the difficulties with cyanide (which induces marked high leads to low spin spectral shifts in cytochrome a33+) and azide (which induces peak shifts of cytochrome a2+ towards the blue in both alpha- and Soret regions). 3. The rate of formate dissociation from cytochrome a2+ a33+ -HCOOH is faster than its rate of dissociation from a3+ a33+ -HCOOH, especially in the presence of cytochrome c. The Ki for formate inhibition of respiration is a function of the reduction state of the system, varying from 30 mM (100% reduction) to 1 mM (100% oxidation) at pH 7.4, 30 degrees C. 4. Succinate-cytochrome c reductase activity is also inhibited by formate, in a reaction competitive with succinate and dependent on [formate]2. 5. Formate inhibition of ascorbate plus N, N, N', N'-tetramethyl-p-phenylenediamine oxidation by intact rat liver mitochondria is partially released by uncoupler addition. Formate is permeable through the inner mitochondrial membrane and no differences in 'on' or 'off' inhibition rates were observed when intact mitochondria were compared with submitochondrial particles. 6. NADH-cytochrome c reductase activity is unaffected by formate in submitochondrial particles, but mitochondrial oxidation of glutamate plus malate is subject both to terminal inhibition at the cytochrome aa3 level and to a slow extra inhibition by formate following uncoupler addition, indicating a third site of formate action in the intact mitochondrion.
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PMID:The effect of formate on cytochrome aa3 and on electron transport in the intact respiratory chain. 0 41

Hepatic microsomes from rats fed a crude or a purified diet were compared by measureing their contents of protein, cytochrome P-450, and cytochrome b5, their rates of activity of NADPH- and NADH-cytochrome c reductases, NADPH-cytochrome P-450 reductase, NADPH oxidase, lipid peroxidase, ethylmorphine N-demethylase, aniline hydroxylase, benzpyrene hydroxylase, and their substrate-binding spectra (ethylmorphine, hexobarbital, aniline, and ethyl isoyanide). With the exception of lipid peroxidase activity, which was much higher in microsomes from animals fed the crude diet, little or no consistent diet-related differences in these measurements were observed over a 4-week experimental period, nor were results significantly less variable with one or the other diet. No consistent significant differences were observed with two strains of rats. The lower lipid peroxidase activity seen with the purified diet appeared to be due to the high vitamin E intake when that diet was employed; rats fed the crude diet and an oral supplement of alpha-tocopherol yielded microsomes with low lipid peroxidase activities similar to those seen in microsomes from rats fed the purified diet. A gradual temporal increase in benzpyrene hydroxylase activity was observed with both diets. This was interpreted to be due to environment inducing agents other than those present in the diet.
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PMID:Comparison of hepatic microsomal drug-metabolizing systems from rats fed crude and purified diets. 0 25

Anaerobic reduction of the flavoprotein adrenodoxin reductase with NADPH yields a spectrum with long wavelength absorbance, 750 nm and higher. No EPR signal is observed. This spectrum is produced by titration of oxidized adrenodoxin reductase with NADPH, or of dithionite-reduced adrenodoxin reductase with NADP+. Both titrations yield a sharp endpoint at 1 NADP(H) added per flavin. Reduction with other reductants, including dithionite, excess NADH, and catalytic NADP+ with an NADPH generating system, yields a typical fully reduced flavin spectrum, without long wavelength absorbance. The species formed on NADPH reduction appears to be a two-electron-containing complex, with a low dissociation constant, between reduced adrenodoxin reductase and NADP+, designated ARH2-NADP+. Titration of dithionite-reduced adrenodoxin reductase with NADPH also produces a distinctive spectrum, with a sharp endpoint at 1 NADPH added per reduced flavin, indicating formation of a four-electron-containing complex between reduced adrenodoxin reductase and NADPH. Titration of adrenodoxin reductase with NADH, instead of NADPH, provides a curved titration plot rather than the sharp break seen with NADPH, and permits calculation of a potential for the AR/ARH2 couple of -0.291 V, close to that of NAD(P)H (-0.316 V). Oxidized adrenodoxin reductase binds NADP+ much more weakly (Kdiss=1.4 X 10(-5) M) than does reduced adrenodoxin reductase, with a single binding site. The preferential binding of NADP+ to reduced enzyme permits prediction of a more positive oxidation-reduction potential of the flavoprotein in the presence of NADP+; a change of about + 0.1 V has been demonstrated by titration with safranine T. From this alteration in potential, a Kdiss of 1.0 X 10(-8) M for binding of NADP+ to reduced adrenodoxin reductase is calculated. It is concluded that the strong binding of NADP+ to reduced adrenodoxin reductase provides the thermodynamic driving force for formation of a fully reduced flavoprotein form under conditions wherein incomplete reduction would otherwise be expected. Stopped flow studies demonstrate that reduction of adrenodoxin reductase by equimolar NADPH to form the ARH2-NADP+ complex is first order (k=28 s-1). When a large excess of NADPH is used, a second apparently first order process is observed (k=4.25 s-1), which is interpreted as replacement of NADPH for NADP+ in the ARH2-NADP+ complex. Comparison of these rate constants to catalytic flavin turnover numbers for reduction of various oxidants by NADPH, suggests an ordered sequential mechanism in which reduction of oxidant is accomplished by the ARH2-NADP+ complex, followed by dissociation of NADP+. The absolute dependence of NADPH-cytochrome c reduction on both adrenodoxin reductase and adrenodoxin is confirmed...
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PMID:Adrenodoxin reductase. Properties of the complexes of reduced enzyme with NADP+ and NADPH. 0 75

The cytochrome oxidase (EC 1.9.3.1) of Rhodopseudomonas palustris was extracted with Triton X-100 plus KCl, from the membrane fraction of cells grown aerobically in the dark. The solubilized enzyme was purified by (NH4)2SO4 precipitation and chromatography on DEAE-cellulose. The purification resulted in a 108-fold enrichment of cytochrome oxidase on the basis of specific activity when compared to the membrane fraction. The purified enzyme was phosphate-sensitive (less than mM), oxidized reduced bovine, horse and yeast cytochrome c, and was inhibited 50% by 0.5 muM KCN or 7 muM NaN3. The native purified preparation migrated as one band in polyacrylamide gel electrophoresis. In the presence of dodecylsulfate four major polypeptides with apparent molecular weights of 30500, 25500, 12200 and 9500 were observed. The enzyme reacted with oxygen via cytochrome o. The purified preparation contained cytochrome c but was free of flavoproteins and NADH-linked and succinate-linked enzyme activities of the respiratory chain.
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PMID:Isolation and partial characterization of the cytochrome oxidase from Rhodopseudomonas palustris. 0 86

1. Increasing the substrate concentration only decreased the inhibition of mitochondrial oxidations by diphenyleneiodonium or by 2,4-dichlorophenyleneiodonium by a small amount. 2. Diphenyleneiodonium and 2,4-dichlorodiphenyleneiodonium lowered the amounts of succinate, citrate and glutamate accumulated in the matrix of mitochondria in the presence of Cl-, but not in its absences. 2,4-Dichlorodiphenyleneiodonium decreased the accumulation of substrates by mitochondria oxidizing glycerol 3-phosphate. 3. Diphenyleneiodonium caused an alkalinization of the medium with an anaerobic suspension of mitochondria, which was only partly reversed by Triton X-100. 4. The rate of proton extrusion by mitochondria oxidizing succinate was not altered by diphenyleneiodonium or by 2,4-dichlorodiphenyleneiodium, although the rate of decay of proton pulses was increased. 5. 2,4-Dichlorodiphenyleneiodonium shifted the pH optimum for succinate oxidation by intact mitochondria from pH 7.2 to 8.0, whereas there was no effect on that of freeze-thawed mitochondria, which was pH 8.0. 6. The concentration of 2,4-dichlorophenyleneiodonium required to inhibit respiration by 50% is less the higher the absolute rate of oxygen uptake. 7. EDTA, but not EGTA [ethanedioxybis(ethylamine)-tetra-acetic acid] increased the inhibition of respiration by diphenyleneiodonium, 2,4-dichlorodiphenyleneiodonium and by tri-n-propyltin. 8. It is concluded that diphenyleneiodonium and 2,4-dichlorodiphenyleneiodonium limit respiration in Cl--containing medium by causing an acidification of the matrix, and that there are pH-sensitive sites in the respiratory chain between NADH and succinate, and between succinate and cytochrome c.
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PMID:The effects of diphenyleneiodonium and of 2,4-dichlorodiphenyleneiodonium on mitochondrial reactions. Mechanism of the inhibition of oxygen uptake as a consequence of the catalysis of the chloride/hydroxyl-ion exchange. 1 Aug 93

Adrenodoxin reductase and adrenodoxin have been shown (Chu, J.-W., and Kimura, T. (1973) J. Biol. Chem. 248, 5183-5187) to form a low dissociation constant, 1:1 complex when both proteins are in the oxidized form. We have found that when adrenodoxin: adrenodoxin reductase ratios are varied by increasing the adrenodoxin concentration, with adrenodoxin reductase held constant, an increasing rate of cytochrome c reduction, with NADPH as reductant, is seen up to a ratio of 1:1, indicating that cytochrome c reduction occurs via the protein-protein complex. Spectra observed during titration of this protein-protein complex with NADH were resolved into components by the linear programming method, using a computer program written in Fortran IV. Analysis of the data has shown that the flavoprotein is reduced prior to the iron sulfur protein, and that the midpoint oxidation-reduction potentials (pH 7.5) of the two proteins are -295 and -331 mV, respectively, when both are present in the complex. Complex formation does not alter the potential of adrenodoxin reductase, but changes that of adrenodoxin by -40 mV. Equilibrium constants derived from potential measurements show that the strength of the protein-protein interaction in the complex is unaltered by reduction of adrenodoxin reductase, but is decreased by about 1 kcal due to reduction of adrenodoxin. The low dissociation constants for both oxidized reduced forms of the adrenodoxin reductase-adrenodoxin complex indicate that the complex must remain associated throughout its catalytic cycle. Titration of the adrenodoxin reductase-adrenodoxin complex with the physiologic reductant, NADPH, was followed by EPR and visible spectra, and yielded an order of reduction of the components identical with that seen when NADH was used as reductant. Reduction of the protein-protein complex with NADPH yielded a ternary complex between NADP+, flavoprotein, and iron sulfur protein, with the two electrons located in a "charge transfer" complex between flavoprotein and pyridine nucleotide.
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PMID:Adrenodoxin reductase-adrenodexin complex. 1 71

The presence of NADH-cytochrome b5 reductase [EC 1.6.2.2] in microsomes from anaerobically grown yeast was confirmed by its isolation and purification. The purified preparation of the reductase showed an apparent molecular weight of 27,000 daltons. The reductase appeared to contain loosely-bound FAD as a prosthetic group. The reductase required NADH as a specific electron donor, and could reduce some redox dyes as well as cytochrom b5. The reductase, however, could not reduce cytochrome c. Michaelis constants of the reductase for NADH and calf liver cytochrome b5 were 6.3 and 1.5 micron M, respectively, and optimal pH for cytochrome b5 reduction was 5.6. Although some differences exist between the properties of NADH-cytochrome b5 reductase from yeast and from mammalia, the results indicate a functional similarity of the present enzyme to mammalian NADH-cytochrome b5 reductase in the microsomal electron-transport system.
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PMID:Studies on the microsomal electron-transport system of anaerobically grown yeast. IV. Purification and characterization of NADH-cytochrome b5 reductase. 1 30


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