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:1.6.99.5 (NADH dehydrogenase)
2,135 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The components involved in the respiratory system of the euryarcheon Halobacterium salinarum were investigated by spectroscopic and polarographic techniques. Previous results about the cytochrome composition could be verified. However, under low oxygen tension, the expression of a d-type cytochrome was detected. Membranes exerted an NADH- and succinatecytochrome-c oxidoreductase as well as an NADH and succinate oxidase activity. These activities could be blocked by the following inhibitors: 7-jodocarboxylic acid, giving evidence for the presence of a type II NADH dehydrogenase, antimycin A, and myxothiazol, indicating the presence of a complex III analog, and the typical succinate dehydrogenase (SDH) and terminal oxidase inhibitors. Complex I inhibitors like rotenone and annonine were inactive, clearly excluding the presence of a coupled NADH dehydrogenase. In addition, no [Fe-S] resonances in the region of the NADH dehydrogenase (NDH) clusters could be observed after NADH addition. One of the terminal oxidases could be shown to act as a cytochrome-c oxidase with a Km value of 37 microM and an activation energy of 23.7 kJ/mol. The relative molecular mass of the endogenous c-type cytochrome could be determined as 14.1 kD. The complex III analog could be enriched after detergent extraction with Triton X-100 and hydroxylapatite (HTP) chromatography. The partially purified complex contained a Rieske iron-sulfur cluster, b- and c-type cytochromes, and was catalytically active in the decylubiquinone-cytochrome-c oxidoreductase assay.
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PMID:Studies of the electron transport chain of the euryarcheon Halobacterium salinarum: indications for a type II NADH dehydrogenase and a complex III analog. 993 47

The fitness of organisms depends upon the rate at which they generate superoxide (O-2) and hydrogen peroxide (H2O2) as toxic by-products of aerobic metabolism. In Escherichia coli these oxidants arise primarily from the autoxidation of components of its respiratory chain. Inverted vesicles that were incubated with NADH generated O-2 and H2O2 at accelerated rates either when treated with cyanide or when devoid of quinones, implicating an NADH dehydrogenase as their source. Null mutations in the gene encoding NADH dehydrogenase II averted autoxidation of vesicles, and its overproduction accelerated it. Thus NADH dehydrogenase II but not NADH dehydrogenase I, respiratory quinones, or cytochrome oxidases formed substantial O-2 and H2O2. NADH dehydrogenase II that was purified from both wild-type and quinone-deficient cells generated approximately 130 H2O2 and 15 O-2 min-1 by autoxidation of its reduced FAD cofactor. Sulfite reductase is a second autoxidizable electron transport chain of E. coli, containing FAD, FMN, [4Fe-4S], and siroheme moieties. Purified flavoprotein that contained only the FAD and FMN cofactors had about the same oxidation turnover number as did the holoenzyme, 7 min-1 FAD-1. Oxidase activity was largely lost upon FMN removal. Thus the autoxidation of sulfite reductase, like that of the respiratory chain, occurs primarily by autoxidation of an exposed flavin cofactor. Great variability in the oxidation turnover numbers of these and other flavoproteins suggests that endogenous oxidants will be predominantly formed by only a few oxidizable enzymes. Thus the degree of oxidative stress in a cell may depend upon the titer of such enzymes and accordingly may vary with growth conditions and among different cell types. Furthermore, the chemical nature of these reactions was manifested by their acceleration at high temperatures and oxygen concentrations. Thus these environmental parameters may also directly affect the O-2 and H2O2 loads that organisms must bear.
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PMID:The identification of primary sites of superoxide and hydrogen peroxide formation in the aerobic respiratory chain and sulfite reductase complex of Escherichia coli. 1018 94

In plant-dwelling trypanosomatids from the genus Phytomonas, mitochondrial functions, such as cytochrome mediated respiration, ATP production and Krebs cycle, are missing, and cell energetics is based on the glycolysis. Using Blue Native/Tricine-SDS two-dimensional gel electrophoretic analysis, we observed that mitochondrial respiratory Complexes III (cytochrome bc1) and IV (cytochrome c oxidase) were absent in Phytomonas serpens; however, Complex V (ATPase) was present. A deletion of the genes for cytochrome c oxidase subunit III (COIII) and apocytochrome b (Cyb) was identified within the 6234 bp sequenced region of the 31 kb maxicircle kinetoplast DNA. Genes, found in this region, include 12S and 9S ribosomal RNAs, subunits 7, 8 and 9 of NADH dehydrogenase (ND7, ND8 and ND9) and subunit 6 of ATPase (A6 or MURF4), as well as the genes (MURF1, MURF5 and G3) with unknown function. Most genes are actively transcribed and some mRNAs are edited. Fully edited mRNAs for A6 and G3 were abundant, while edited ND7 transcripts were rare, and only partially edited and pre-edited transcripts for ND8 were detected. The data show that the mitochondrial genome of P. serpens is functional, although its functions may be limited to expressing the ATPase and, possibly, NADH dehydrogenase complexes.
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PMID:Partial kinetoplast-mitochondrial gene organization and expression in the respiratory deficient plant trypanosomatid Phytomonas serpens. 1034 Apr 85

The effect of maesaquinone, 2-(14-nonadecenyl)-3,6-dihydroxy-5-methyl-1,4-benzoquinone, on plant mitochondrial respiration has been investigated. In mitochondria isolated from thermogenic Arum maculatum spadices, this compound inhibits both cytochrome and alternative pathway activities. Kinetic analyses reveal that this inhibition is the result of potent effects of maesaquinone on the alternative oxidase (ID50 < 0.3 microM) and complex III (ID50 < 5 microM). Succinate dehydrogenase and external NADH dehydrogenase are also inhibited, albeit to a lesser extent (approximately 30% at 1 microM). These data suggest that maesaquinone specifically affects the interaction of the respective enzymes with ubiquinone.
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PMID:Maesaquinone: a novel inhibitor of plant mitochondrial respiratory enzymes that react with ubiquinone. 1103 48

The sensitivity of Venturia inaequalis field isolates to inhibitors of the cytochrome bc1 complex at the Qo site (QoIs) was characterised at the molecular, biochemical and physiological level, and compared to other respiration inhibitors. Comparison of a sensitive and a QoI-resistant isolate revealed very high resistance factors both in mycelium growth and spore germination assays. Cross-resistance was observed among QoIs such as trifloxystrobin, azoxystrobin, famoxadone, strobilurin B and myxothiazol. In the mycelium growth assay, antimycin A, an inhibitor of the cytochrome bc1 complex at the Qi site, was less active against the QoI-resistant than against the sensitive isolate. The mixture of QoIs with salicylhydroxamic acid (SHAM), an inhibitor of the alternative oxidase, exerted synergistic effects in the spore germination but not in the mycelium growth assay. Thus, the cytochrome and the alternative respiration pathways are assumed to play different roles, depending on the developmental stage of the fungus. Induction of alternative oxidase (AOX) by trifloxystrobin was observed in mycelium cells at the molecular level for the sensitive but not the resistant isolate. Following QoI treatment, respiration parameters such as oxygen consumption, ATP level, membrane potential and succinate dehydrogenase activity were only slightly reduced in Qo-resistant mycelium cells, and remained at much higher levels than in sensitive cells. In contrast, no difference was observed between sensitive and resistant isolates when NADH consumption was measured. Comparison of the cytochrome b (cyt b) gene of the sensitive and resistant isolates did not reveal any point mutations as is known to occur in resistant isolates of other plant pathogens. It is assumed that QoI resistance in V inaequalis may be based on a compensation of the energy deficiency following QoI application upstream of the NADH dehydrogenase of the respiratory chain.
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PMID:Sensitivity of mitochondrial respiration to different inhibitors in Venturia inaequalis. 1156 3

Ubiquinone is inhomogeneously distributed in subcellular biomembranes. Apart from mitochondria, where ubiquinone was demonstrated to exert bioenergetic and pathophysiological functions, unusually high levels of ubiquinone were also reported to exist in Golgi vesicles and lysosomes. In lysosomes the interior differs from other organelles by the low pH value which is important not only to arrest proteins but also to ensure optimal activity of proteases. Since redox cycling of ubiquinone is associated with the acceptance and release of protons, we assumed that ubiquinone is a part of a redox chain contributing to unilateral proton distribution. A similar function of ubiquinone was earlier reported to exist in Golgi vesicles. Support for the involvement of ubiquinone in a presumed couple of redox carriers came from our observation that almost 70% of total lysosomal ubiquinone was in the divalently reduced state. Further reduction was seen in the presence of external NADH. Analysis of the components involved in the transfer of reducing equivalents from cytosolic NADH to ubiquinone revealed the existence of a flavin adenine dinucleotide-containing NADH dehydrogenase. The latter was found to reduce ubiquinone by means of a b-type cytochrome. Proton translocation into the interior was linked to the activity of the novel lysosomal redox chain. Oxygen was found to be the terminal electron acceptor thereby also regulating acidification of the lysosomal matrix. The role of the proton-pumping redox chain has to be elucidated.
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PMID:The existence and significance of redox-cycling ubiquinone in lysosomes. 1173 43

When petunia (Petunia hybrida Vilm, cv Rosy Morn) cells are cultured in the presence of 2 [mu]M antimycin A (AA), respiration proceeds mainly via the cyanide-resistant pathway. Cyanide-resistant respiratory rates were higher in mitochondria from AA cells than in control mitochondria. Compared with control cells, an increase in alternative oxidase protein was observed in AA cells, as well as an increase in ubiquinone (UQ) content. A change in the kinetics of succinate dehydrogenase was observed: there was a much higher activity at high UQ reduction in mitochondria from AA cells compared with control mitochondria. No changes were found for external NADH dehydrogenase kinetics. In AA cells in vivo, UQ reduction was only slightly higher than in control cells, indicating that increased electron transport via the alternative pathway can prevent high UQ reduction levels. Moreover, O2 consumption continues at a similar rate as in control cells, preventing O2 danger. These adaptations to stress conditions, in which the cytochrome pathway is restricted, apparently require, in addition to an increase in alternative oxidase protein, a new setup of the relative amounts and/or kinetic parameters of all of the separate components of the respiratory network.
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PMID:Changes in Mitochondrial Respiratory Chain Components of Petunia Cells during Culture in the Presence of Antimycin A. 1222 30

SHAM-sensitive (STO) alternative respiration is present in the xylose-metabolizing, Crabtree-negative yeast, Pichia stipitis, but its pathway components and physiological roles during xylose metabolism are poorly understood. We cloned PsSTO1, which encodes the SHAM-sensitive terminal oxidase (PsSto1p), by genome walking from wild-type CBS 6054 and subsequently deleted PsSTO1 by targeted gene disruption. The resulting sto1-delta deletion mutant, FPL-Shi31, did not contain other isoforms of Sto protein that were detectable by Western blot analysis using an alternative oxidase monoclonal antibody raised against the Sto protein from Sauromatum guttatum. Levels of cytochromes b, c, c(1) and a.a(3) did not change in the sto1-delta mutant, which indicated that deleting PsSto1p did not alter the cytochrome pool. Interestingly, the sto1-delta deletion mutant stopped growing earlier than the parent and produced 20% more ethanol from xylose. Heterologous expression of PsSTO1 in Saccharomyces cerevisiae increased its total oxygen consumption rate and imparted cyanide-resistant oxygen uptake but did not enable growth on ethanol, indicating that PsSto1p is not coupled to ATP synthesis. We present evidence that the mitochondrial NADH dehydrogenase complex (Complex I) was present in wild-type CBS 6054 but was bypassed in the cells during xylose metabolism. Unexpectedly, deleting PsSto1p led to the use of Complex I in the mutant cells when xylose was the carbon source. We propose that the non-proton-translocating NAD(P)H dehydrogenases are linked to PsSto1p in xylose-metabolizing cells and that this non-ATP-generating route serves a regulatory function in the complex redox network of P. stipitis.
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PMID:SHAM-sensitive alternative respiration in the xylose-metabolizing yeast Pichia stipitis. 1227 57

Combined transcriptome and proteome analysis was carried out to understand metabolic and physiological changes of Escherichia coli during the high cell density cultivation (HCDC). The expression of genes of TCA cycle enzymes, NADH dehydrogenase and ATPase, was up-regulated during the exponential fed-batch period and was down-regulated afterward. However, expression of most of the genes involved in glycolysis and pentose phosphate pathway was up-regulated at the stationary phase. The expression of most of amino acid biosynthesis genes was down-regulated as cell density increased, which seems to be the major reason for the reduced specific productivity of recombinant proteins during HCDC. The expression of chaperone genes increased with cell density, suggesting that the high cell density condition itself can be stressful to the cells. Severe competition for oxygen at high cell density seemed to make cells use cytochrome bd, which is less efficient but has a high oxygen affinity than cytochrome bo(3). Population cell density itself strongly affected the expression of porin protein genes, especially ompF, and hence the permeability of the outer membrane. Expression of phosphate starvation genes was most strongly up-regulated toward the end of cultivation. It was also found that sigma(E) (rpoE) plays a more important role than sigma(S) (rpoS) at the stationary phase of HCDC. These findings should be invaluable in designing metabolic engineering and fermentation strategies for the production of recombinant proteins and metabolites by HCDC of E. coli.
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PMID:Combined transcriptome and proteome analysis of Escherichia coli during high cell density culture. 1255 8

Three rotenone-insensitive NADH dehydrogenases are present in the mitochondria of yeast Saccharomyces cerevisiae, which lack complex I. To elucidate the functions of these enzymes, superoxide production was determined in yeast mitochondria. The low levels of hydrogen peroxide (0.10 to 0.18 nmol/min/mg) produced in mitochondria incubated with succinate, malate, or NADH were stimulated 9-fold by antimycin A. Myxothiazol and stigmatellin blocked completely hydrogen peroxide formation with succinate or malate, indicating that the cytochrome bc(1) complex is the source of superoxide; however, these inhibitors only inhibited 46% hydrogen peroxide formation with NADH as substrate. Diphenyliodonium inhibited hydrogen peroxide formation (with NADH as substrate) by 64%. Superoxide formation, determined by EPR and acetylated cytochrome c reduction in mitochondria was stimulated by antimycin A, and partially inhibited by myxothiazol and stigmatellin. Proteinase K digestion of mitoplasts reduced 95% NADH dehydrogenase activity with a similar inhibition of superoxide production. Mild detergent treatment of the proteinase-treated mitoplasts resulted in an increase in NADH dehydrogenase activity due to the oxidation of exogenous NADH by the internal NADH dehydrogenase; however, little increase in superoxide production was observed. These results suggest that the external NADH dehydrogenase is a potential source of superoxide in S. cerevisiae mitochondria.
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PMID:External alternative NADH dehydrogenase of Saccharomyces cerevisiae: a potential source of superoxide. 1256 73


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