Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.3 (complex I)
 8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

1. An NADH-ferricyanide reductase activity has been isolated from the respiratory chain of Torulopsis utilis by using detergents. The isolated enzyme contains non-haem iron, acid-labile sulphide and FMN in the molar proportions 27.5:28.4:1. The preparation is free of FAD and largely free of cytochrome. 2. The enzyme catalyses ferricyanide reduction by NADPH at about 1% of the rate with NADH, and reacts poorly with acceptors other than ferricyanide. The rates of reduction of some acceptors are, as percentages of the rate with ferricyanide: menadione, 0.35%; lipoate, 0.01%; cytochrome c, 0.065%; dichlorophenolindophenol, 0.35%; ubiquinone-1, 0.08%. 3. Several properties of submitochondrial particles of T. utilis (non-haem iron, acid-labile sulphide, FMN and an NADH-reducible electron-paramagnetic-resonance signal) were found to co-purify with the NADH-ferricyanide reductase activity. Thus about 70% of the FMN and, within the limits of accuracy of the experiments, 100% of the non-haem iron and acid-labile sulphide of submitochondrial particles derived from T. utilis cells grown under conditions of glycerol limitation (but relatively low iron availability) can be attributed to the NADH-ferricyanide reductase. 4. It was also shown that the component of submitochondrial particles specifically bleached at 460nm by NADH [species 1 of Ragan & Garland (1971)] co-purifies with the NADH-ferricyanide reductase. 5. This successful purification of an NADH dehydrogenase from T. utilis forms a starting point for investigating the molecular properties of phenotypically modified mitochondrial NADH oxidation pathways that lack energy conservation between NADH and the cytochromes.
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PMID:The purification and properties of the respiratory-chain reduced nicotinamide--adenine dinucleotide dehydrogenase of Torulopsis utilis. 439 88

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

NADH dehydrogenase [EC 1.6.99.3] in membranes of Bacillus caldotenax was solubilized with sodium N-lauroylsarcosinate and purified 50-fold from membranes to 75-80% homogeneity, as judged by SDS-polyacrylamide gel electrophoresis. The enzyme was considered to be located on the electron transport chain and to be an FAD-containing protein. The molecular weight of the subunit was estimated to be 44,000. The enzyme (or the enzyme bound to the B. caldotenax membrane lipids) follows a ping-pong mechanism. The enzyme can oxidize NADH, but not NADPH, with 2,6-dichlorophenol indophenol, ferricyanide, menadione, and cytochrome c as electron acceptors. Membrane lipids or Triton X-100 stimulated the enzyme activity, except that with menadione. Lipids decreased the apparent affinity of electron acceptors and NADH to the enzyme, and increased the maximum velocity, except when menadione was used as the electron acceptor. Lipids partially protected the enzyme from thermal inactivation. The enzyme exhibited a continuous Arrhenius plot, while the lipids- or membrane-bound enzyme exhibited a discontinuous plot.
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PMID:Effect of lipids on a membrane-bound NADH dehydrogenase from Bacillus caldotenax. 616 6

This investigation examined the effect of the anthracycline antitumor agents on reactive oxygen metabolism in rat heart. Oxygen radical production by doxorubicin, daunorubicin, and various anthracycline analogues was determined in heart homogenate, sarcoplasmic reticulum, mitochondria, and cytosol, the major sites of cardiac damage by the anthracycline drugs. Superoxide production in heart sarcosomes was significantly increased by anthracycline treatment; for doxorubicin, the reaction appeared to follow saturation kinetics with an apparent Km of 112.62 microM, required NADPH as cofactor, was accompanied by the accumulation of hydrogen peroxide, and probably resulted from the transfer of electrons to molecular oxygen by the doxorubicin semiquinone after reduction of the drug by sarcosomal NADPH:cytochrome P-450 reductase (NADPH:ferricytochrome oxidoreductase, EC 1.6.2.4). Superoxide formation was also significantly enhanced by the anthracycline antibiotics in the mitochondrial fraction. Doxorubicin stimulated mitochondrial superoxide formation in a dose-dependent manner that also appeared to follow saturation kinetics (apparent Km of 454.55 microM); however, drug-related superoxide production by mitochondria required NADH rather than NADPH and was significantly increased in the presence of rotenone, which suggested that the proximal portion of the mitochondrial NADH dehydrogenase complex [NADH:(acceptor) oxidoreductase, EC 1.6.99.3] was responsible for the reduction of doxorubicin at this site. In heart cytosol, anthracycline-induced superoxide formation and oxygen consumption required NADH and were significantly reduced by allopurinol, a potent inhibitor of xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2). Reactive oxygen production was detected in all of our studies despite the presence of both superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) and glutathione peroxidase (glutathione:hydrogen peroxide oxidoreductase, EC 1.11.1.9) in each cardiac fraction. These results suggest that free radical formation by the anthracycline antitumor agents, which occurs in the same myocardial compartments that are subject to drug-induced tissue injury, may damage the heart by exceeding the oxygen radical detoxifying capacity of cardiac mitochondria and sarcoplasmic reticulum.
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PMID:Effect of anthracycline antibiotics on oxygen radical formation in rat heart. 629 97

Stimulation of the rates of NAD(P)H oxidation, superoxide generation, and hydrogen peroxide formation by three anthracenedione antineoplastic agents in the presence of NADPH-cytochrome P-450 reductase, NADH dehydrogenase, or rabbit hepatic microsomes was studied and the results compared with those obtained for the anthracyclines Adriamycin and daunorubicin. In all cases the anthracenediones, including mitoxantrone and ametantrone, were significantly (5- to 20-fold) less effective than the anthracyclines in stimulating NAD(P)H oxidation, superoxide formation, or hydrogen peroxide production. Of the three anthracenediones studied, the ring-monohydroxylated compound showed the greatest activity followed by the ring-dihydroxylated derivative (mitoxantrone). In contrast, the non-ring-hydroxylated anthracenedione (ametantrone) was a relatively ineffective electron acceptor and inhibited the reduction of more effective acceptors such as Adriamycin. Michaelis-Menten kinetic constants were determined by analysis of the rates of NADPH oxidation. NADP+ and 2'-AMP inhibited the reduction of the ring-hydroxylated anthracenediones and anthracyclines, demonstrating the enzymatic nature of the reaction. The non-ring-hydroxylated anthracenedione inhibited the reduction of Adriamycin by both P-450 reductase and NADH dehydrogenase with 50% inhibition achieved at approximately 300 microM. Thus, there appears to exist a structural relationship between anthracenedione ring hydroxylation and metabolic activation. These results also suggest that the relative inability of the anthracenediones to function as artificial electron acceptors in comparison to the anthracyclines may be correlated with diminished anthracenedione cardiotoxicity.
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PMID:Bis(alkylamino)anthracenedione antineoplastic agent metabolic activation by NADPH-cytochrome P-450 reductase and NADH dehydrogenase: diminished activity relative to anthracyclines. 640 91

The oxidative and phosphorylative properties of mitochondria isolated from Neurospora crassa were investigated as a function of growth stage. The rates of oxidation of exogenous NADH and NADPH varied independently of each other, thus ruling out the existence of only one unspecific dehydrogenase. Two different pathways were involved in the oxidation of NAD-linked substrates, as indicated by changes in the rate of oxygen uptake, the sensitivity to rotenone, and the efficiency of phosphorylation. One pathway was sensitive to rotenone and involved three energy-coupling sites, whereas the other was resistant to rotenone and bypassed complex I. Our results indicated that the activity of complex I of the respiratory chain increased markedly in the late exponential phase of growth, remained high in the stationary phase, and then decreased when conidiae were formed. In contrast, the activity of the rotenone-resistant bypass was maximal in the early exponential phase. With malate (plus glutamate) as a substrate, the sensitivity to rotenone and the ADP/O ratios were always lower than those observed with other NAD-linked substrates, suggesting a possible cooperation between malate dehydrogenase and the rotenone-resistant pathway. The rate of oxygen uptake measured in the presence of rotenone was significantly increased by the addition of exogenous NAD+, suggesting that added NAD+ could interact with the rotenone-resistant bypass.
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PMID:Properties of mitochondria as a function of the growth stages of Neurospora crassa. 646 22

Extracellularly applied NADH, but not NAD or NADPH, increases the resting membrane potential from -74.1 to -76.6 mV in freshly isolated muscles in the presence of K+ in the incubation medium and from -64.6 to -72.9 mV in muscles equilibrated for 4-6 h in a K+-free solution. The NADH-induced hyperpolarization is blocked by pretreatment of muscles with ouabain, and the inhibitors of plasma membrane NADH dehydrogenase (adriamycin, azide, PCMB, atebrine, DIDS and bleomycin). The effect of NADH is accompanied by the disappearance of NADH from the incubation medium and by decreased membrane resistance. We conclude that NADH hyperpolarization is due to the enhancement of passive membrane permeability, apparently for K+, which might result from the conformational changes in the plasma membrane during the NADH dehydrogenase reaction. The possibility is discussed that NADH dehydrogenase mediates transport of K+ out from the cell using a pathway connected with the transmembrane Na+/K+ pump.
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PMID:Hyperpolarization of mouse skeletal muscle plasma membrane induced by extracellular NADH. 646 61

An NADH-cytochrome c reductase (complex I-III) was isolated from Ascaris suum muscle mitochondria. The enzyme preparation catalyzed the reduction of 1.68 mumol cytochrome c min-1 mg-1 protein at 25 degrees C with NADH but not with NADPH, and retained its sensitivity to rotenone, piericidin A and 2-heptyl-4-hydroxyquinoline-N-oxide as with the submitochondrial particles. The isolated complex I-III, essentially free of succinate-cytochrome c reductase and cytochrome c oxidase, consisted of fourteen polypeptides with apparent molecular weights ranging from 76 000 to 12 000. The complex I-III contained three cytochromes, b-559.5, b-563 and c1-550.5 and Pigment-558 at concentrations of 1.28, 0.211, 1.23 and 0.321 nmol mg-1 protein, respectively. Cytochrome b-558, a major constituent cytochrome of Ascaris mitochondria and previously suggested to participate in the fumarate reductase system, was not fractionated in the complex I-III. Localization of the cytochromes in Ascaris electron transfer complexes is discussed.
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PMID:Electron transfer complexes of Ascaris suum muscle mitochondria: I. Characterization of NADH-cytochrome c reductase (complex I-III), with special reference to cytochrome localization. 651 90

The addition of a purified mitochondrial pyridine nucleotide transhydrogenase enzyme preparation to complex I (NADH-CoQ reductase) results in a significant increase in the NADPH-AcPyAD+ transhydrogenase activity of the complex without influencing the NADH-AcPyAD+ transhydrogenase activity. When subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of complex I, the purified transhydrogenase enzyme preparation was found to co-migrate with the Mr = 130,000 (130K) subunit of the NADH-CoQ reductase. Loss of the NADPH-NAD+ transhydrogenase activity of complex I following limited tryptic digestion was associated with a corresponding loss of the 130K subunit from the complex. These results suggest that the 130K subunit of complex I is the specific peptide responsible for the catalysis of the NADPH-NAD+ transhydrogenase activity observed in complex I. Studies have been carried out testing the influence of photoaffinity pyridine nucleotide probes on the NADPH-NAD+ transhydrogenase activity catalyzed at three levels of resolution, i.e. a homogeneous transhydrogenase preparation, a partially resolved membrane preparation (complex I), and an intact mitochondrial membrane preparation (EDTA particles). Such studies have revealed arylazido-beta-alanyl NADP+ (N3'-O-(3-[N-(4-azido-2-nitrophenyl)amino]propionyl)NADP+) to be a potent inhibitor and an active site-directed reagent for NADPH-NAD+ transhydrogenation at all three levels of resolution. On the other hand, arylazido-beta-alanyl NAD+ (A3'-O-(3-[N-(4-azido-2-nitrophenyl)-amino]propionyl)NAD+ does not produce a significant degree of inhibition of NADPH-NAD+ transhydrogenase activities prior to or following photoirradiation. Nevertheless, the NAD+ analogue has been found to specifically label, covalently, the transhydrogenase protein following photoirradiation of an enzyme-analogue mixture. Arylazido-beta-alanyl NAD+ can as well function as a substrate during transhydrogenation by virtue of being able to accept a hydride ion from NADPH. An interpretation of the observed nucleotide photoprobe specificity for interaction at the active site for transhydrogenation is advanced. In this interpretation, an ordered binding of substrate involves an initial NADP(H) (or NADP+ photoprobe) interaction with a hydrophobic region at the transhydrogenation site. This initial reactivity is followed by a positioning of NAD(H) (or the NAD+ photoprobe analogue) above or periphery to the NADP(H) nucleotide present at the active site region. Supportive evidence for this model for transhydrogenation is presented and discussed.
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PMID:The reaction mechanism of the mitochondrial pyridine nucleotide transhydrogenase. A study utilizing arylazido-pyridine nucleotide analogues. 671 79


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