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 generation of oxygen free radicals was investigated using cytochemistry and its energy-filtering transmission electron microscopy in reference to the toxic mediator for the herbicide paraquat. When isolated intact mitochondria from rat livers were incubated in a medium containing paraquat and NADH, a mitochondrial NADH-quinone oxidoreductase activity generated superoxide anions to cause the destruction of mitochondria which resulted in cell death. The superoxide anions were immediately converted into hydrogen peroxide, which then formed cerium perhydroxide deposits in the presence of cerium ions and precipitated on the outer surface of the mitochondrial outer membrane. This localization was also specifically identified by energy spectral imaging and image-electron energy loss spectral analyses. Precipitation reaction was scavenged by the addition of either cytochrome c or catalase and inhibited by dicoumarol (an inhibitor of NAD(P)H-quinone oxidoreductases). These cytochemical energy-filtering transmission electron microscopic results indicated that paraquat generated free radicals from the outer membrane of mitochondria.
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PMID:Cytochemical energy-filtering transmission electron microscopy of mitochondrial free radical formation in paraquat cytotoxicity. 1042 47

The Synechocystis sp. PCC 6803 triple mutant D2R8 with V247M/A249T/M329I mutations in the D2 subunit of the photosystem II is impaired in Q(A) function, has an apparently mobile Q(A), and is unable to grow photoautotrophically. Several photoautotrophic pseudorevertants of this mutant have been isolated, each of which retained the original psbDI mutations of D2R8. Using a newly developed mapping technique, the site of the secondary mutations has been located in the open reading frame slr0399. Two different nucleotide substitutions and a deletion of about 60% of slr0399 were each shown to restore photoautotrophy in different pseudorevertants of the mutant D2R8, suggesting that inactivation of Slr0399 leads to photoautotrophic growth in D2R8. Indeed, a targeted deletion of slr0399 restores photoautotrophy in D2R8 and in other psbDI mutants impaired in Q(A) function. Slr0399 is similar to the hypothetical protein Ycf39, which is encoded in the cyanelle genome of Cyanophora paradoxa; in the chloroplast genomes of diatoms, dinoflagellates, and red algae; and in the nuclear genome of Arabidopsis thaliana. Slr0399 and Ycf39 have a NAD(P)H binding motif near their N terminus and have some similarity to isoflavone reductase-like proteins and to a subunit of the eukaryotic NADH dehydrogenase complex I. Deletion of slr0399 in wild type Synechocystis sp. PCC 6803 has no significant phenotypic effects other than a decrease in thermotolerance under both photoautotrophic and photomixotrophic conditions. We suggest that Slr0399 is a chaperone-like protein that aids in, but is not essential for, quinone insertion and protein folding around Q(A) in photosystem II. Moreover, as the effects of Slr0399 are not limited to photosystem II, this protein may also be involved in assembly of quinones in other photosynthetic and respiratory complexes.
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PMID:Inactivation of the open reading frame slr0399 in Synechocystis sp. PCC 6803 functionally complements mutations near the Q(A) niche of photosystem II. A possible role of Slr0399 as a chaperone for quinone binding. 1052 36

In the last few years the presence in thylakoid membranes of chloroplasts of a NAD(P)H-plastoquinone oxidoreductase complex (Ndh complex) homologous to mitochondrial complex I has been well established. Herein, we report the identification of the Ndh complex in barley etioplast membranes. Two plastid DNA-encoded polypeptides of the Ndh complex (NDH-A and NDH-F) were relatively more abundant in etioplast membranes than in thylakoids from greening chloroplasts. Conversion of etioplast into chloroplast, after light exposure of barley seedlings grown in the dark, was accompanied by a decrease in the NADH dehydrogenase activity associated to plastid membranes. Using native-PAGE and immunolabelling techniques we have determined that a NADH specific dehydrogenase activity associated with plastid membranes, which was more active in etioplasts than in greening chloroplasts, contained the NDH-A and NDH-F polypeptides. These results complemented by those obtained through blue-native-PAGE indicated that NDH-A and NDH-F polypeptides are part of a 580 kDa NADH dependent dehydrogenase complex present in etioplast membranes. This finding proves that accumulation of the Ndh complex is independent of light. The decrease in the relative levels and specific activity of this complex during the transition from etioplast to chloroplasts was accompanied by a parallel decrease in the specific activity of peroxidase associated to plastid membranes. Based on the mentioned observations it is proposed that an electron transport chain from NADH to H2O2 could be active in barley etioplasts.
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PMID:Identification of the Ndh (NAD(P)H-plastoquinone-oxidoreductase) complex in etioplast membranes of barley: changes during photomorphogenesis of chloroplasts. 1075 Jul 8

Studies of respiration on glucose in procyclic Trypanosoma congolense in the presence of rotenone, antimycin, cyanide, salicylhydroxamic acid and malonate have indicated the presence of NADH dehydrogenase, cytochrome b-c1, cytochrome aa3, trypanosome alternate oxidase and NADH fumarate reductase/succinate dehydrogenase pathway that contributes electrons to coenzyme Q of the respiratory chain. The rotenone sensitive NADH dehydrogenase, the trypanosome alternate oxidase, and cytochrome aa3 accounted for 24.5 +/- 6.5, 36.2 +/- 4.2 and 54.1 +/- 5.5% respectively of the total respiration. Activities of lactate dehydrogenase, NAD(+)-linked malic enzyme and pyruvate kinase were less than 6 nanomoles/min/mg protein suggesting that they play a minor role in energy metabolism of the parasite. Phosphoenolpyruvate carboxykinase, pyruvate dehydrogenase, succinate dehydrogenase, NADP(+)-linked malic enzyme, NADH fumarate reductase, malate dehydrogenase, and alpha-ketoglutarate dehydrogenase and glycerol kinase on the other hand had specific activities greater than 60 nanomoles/min/mg protein. These enzyme activities could account for the production of pyruvate, acetate, succinate and glycerol. The results further show that the amount of glycerol produced was 35-48% of the combined total of pyruvate, acetate and succinate produced. It is apparent that some of the glycerol 3-phosphate produced in glycolysis in the presence of salicylhydroxamic acid is dephosphorylated to form glycerol while the rest is oxidised via cytochrome aa3 to form acetate, succinate and pyruvate.
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PMID:Pathways of glucose catabolism in procyclic Trypanosoma congolense. 1084 79

In Saccharomyces cerevisiae, reduction of NAD(+) to NADH occurs in dissimilatory as well as in assimilatory reactions. This review discusses mechanisms for reoxidation of NADH in this yeast, with special emphasis on the metabolic compartmentation that occurs as a consequence of the impermeability of the mitochondrial inner membrane for NADH and NAD(+). At least five mechanisms of NADH reoxidation exist in S. cerevisiae. These are: (1) alcoholic fermentation; (2) glycerol production; (3) respiration of cytosolic NADH via external mitochondrial NADH dehydrogenases; (4) respiration of cytosolic NADH via the glycerol-3-phosphate shuttle; and (5) oxidation of intramitochondrial NADH via a mitochondrial 'internal' NADH dehydrogenase. Furthermore, in vivo evidence indicates that NADH redox equivalents can be shuttled across the mitochondrial inner membrane by an ethanol-acetaldehyde shuttle. Several other redox-shuttle mechanisms might occur in S. cerevisiae, including a malate-oxaloacetate shuttle, a malate-aspartate shuttle and a malate-pyruvate shuttle. Although key enzymes and transporters for these shuttles are present, there is as yet no consistent evidence for their in vivo activity. Activity of several other shuttles, including the malate-citrate and fatty acid shuttles, can be ruled out based on the absence of key enzymes or transporters. Quantitative physiological analysis of defined mutants has been important in identifying several parallel pathways for reoxidation of cytosolic and intramitochondrial NADH. The major challenge that lies ahead is to elucidate the physiological function of parallel pathways for NADH oxidation in wild-type cells, both under steady-state and transient-state conditions. This requires the development of techniques for accurate measurement of intracellular metabolite concentrations in separate metabolic compartments.
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PMID:Stoichiometry and compartmentation of NADH metabolism in Saccharomyces cerevisiae. 1115 39

Cytosolic redox balance has to be maintained in order to allow an enduring cellular metabolism. In other words, NADH generated in the cytosol has to be re-oxidized back to NAD(+). Aerobically this can be done by respiratory oxidation of cytosolic NADH. However, NADH is unable to cross the mitochondrial inner membrane and mechanisms are required for conveying cytosolic NADH to the mitochondrial electron transport chain. At least two such systems have proved to be functional in S. cerevisiae, the external NADH dehydrogenase (Luttik et al., 1998; Small and McAlister-Henn, 1998) and the G3P shuttle (Larsson et al., 1998). The aim of this investigation was to study the regulation and performance of these two systems in a wild-type strain of S. cerevisiae using aerobic glucose- and nitrogen-limited chemostat cultures. The rate of cytosolic NADH formation was calculated and as expected there was a continuous increase with increasing dilution rate. However, measurements of enzyme activities and respiratory activity on isolated mitochondria revealed a diminishing capacity at elevated dilution rates for both the external NADH dehydrogenase and the G3P shuttle. This suggests that adjustment of in vivo activities of these systems to proper levels is not achieved by changes in amount of protein but rather by, for example, activation/inhibition of existing enzymes. Adenine nucleotides are well-known allosteric regulators and both the external NADH and the G3P shuttle were sensitive to inhibition by ATP. The most severe inhibition was probably on the G3P shuttle, since one of its member proteins, Gpdp, turned out to be exceptionally sensitive to ATP. The external NADH dehydrogenase is suggested as the main system employed for oxidation of cytosolic NADH. The G3P shuttle is proposed to be of some importance at low growth rates and perhaps its real significance is only expressed during starvation conditions.
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PMID:Cytosolic redox metabolism in aerobic chemostat cultures of Saccharomyces cerevisiae. 1132 72

Respiration in cyanobacterial thylakoid membranes is interwoven with photosynthetic processes. We have constructed a range of mutants that are impaired in several combinations of respiratory and photosynthetic electron transport complexes and have examined the relative effects on the redox state of the plastoquinone (PQ) pool by using a quinone electrode. Succinate dehydrogenase has a major effect on the PQ redox poise, as mutants lacking this enzyme showed a much more oxidized PQ pool. Mutants lacking type I and II NAD(P)H dehydrogenases also had more oxidized PQ pools. However, in the mutant lacking type I NADPH dehydrogenase, succinate was essentially absent and effective respiratory electron donation to the PQ pool could be established after addition of 1 mM succinate. Therefore, lack of the type I NADPH dehydrogenase had an indirect effect on the PQ pool redox state. The electron donation capacity of succinate dehydrogenase was found to be an order of magnitude larger than that of type I and II NAD(P)H dehydrogenases. The reason for the oxidized PQ pool upon inactivation of type II NADH dehydrogenase may be related to the facts that the NAD pool in the cell is much smaller than that of NADP and that the NAD pool is fully reduced in the mutant without type II NADH dehydrogenase, thus causing regulatory inhibition. The results indicate that succinate dehydrogenase is the main respiratory electron transfer pathway into the PQ pool and that type I and II NAD(P)H dehydrogenases regulate the reduction level of NADP and NAD, which, in turn, affects respiratory electron flow through succinate dehydrogenase.
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PMID:Succinate dehydrogenase and other respiratory pathways in thylakoid membranes of Synechocystis sp. strain PCC 6803: capacity comparisons and physiological function. 1141 66

Expression of genes for respiratory chain dehydrogenases was investigated in potato (Solanum tuberosum L. cv. Desiree) leaves. The recently characterized nda1 and ndb1 genes, homologues to genes encoding the non-proton pumping respiratory chain NADH-dehydrogenases of Escherichia coli and yeast, were compared to genes encoding catalytic subunits of the proton-pumping NADH dehydrogenase (complex I). As leaves develop from young to mature, the nda1 transcript level increases, accompanied by an elevation in immunodetected NDA protein and internal rotenone-insensitive NADH oxidation. The other investigated transcripts, proteins and NAD(P)H oxidation activities were essentially unchanged. A variation in transcript level, specific for nda1, is seen at different times of the day with highest expression in the morning. This variation also influences the apparent developmental induction. Further, the nda1 mRNA in leaves specifically and completely disappears during dark treatment, with a rapid re-induction when plants are returned to light. Corresponding immunodetected NDA protein is specifically decreased in mitochondria isolated from dark-treated plants, accompanied by a lower capacity for internal rotenone-insensitive NADH oxidation. Complete light dependence and diurnal changes in expression have previously not been reported for genes encoding respiratory chain proteins. Qualitatively similar to NDA, the alternative oxidase showed developmental induction and light dependence. In addition to the specific change in nda1, a general, slower down-regulation in darkness was seen for the other NAD(P)H dehydrogenase genes. The nda1 expression during development, and in response to light, indicates a specific role of the encoded enzyme in the photosynthetically associated mitochondrial metabolism.
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PMID:Light-dependent gene expression for proteins in the respiratory chain of potato leaves. 1169 88

We have studied changes in plasma membrane NAD(P)H:quinone oxidoreductases of HL-60 cells under serum withdrawal conditions, as a model to analyze cell responses to oxidative stress. Highly enriched plasma membrane fractions were obtained from cell homogenates. A major part of NADH-quinone oxidoreductase in the plasma membrane was insensitive to micromolar concentrations of dicumarol, a specific inhibitor of the NAD(P)H:quinone oxidoreductase 1 (NQOI, DT-diaphorase), and only a minor portion was characterized as DT-diaphorase. An enzyme with properties of a cytochrome b5 reductase accounted for most dicumarol-resistant quinone reductase activity in HL-60 plasma membranes. The enzyme used mainly NADH as donor, it reduced coenzyme Q0 through a one-electron mechanism with generation of superoxide, and its inhibition profile by p-hydroxymercuribenzoate was similar to that of authentic cytochrome b5 reductase. Both NQO1 and a novel dicumarol-insensitive quinone reductase that was not accounted by a cytochrome b5 reductase were significantly increased in plasma membranes after serum deprivation, showing a peak at 32 h of treatment. The reductase was specific for NADH, did not generate superoxide during quinone reduction, and was significantly resistant to p-hydroxymercuribenzoate. The function of this novel quinone reductase remains to be elucidated whereas dicumarol inhibition of NQO1 strongly potentiated growth arrest and decreased viability of HL-60 cells in the absence of serum. Our results demonstrate that upregulation of two-electron quinone reductases at the plasma membrane is a mechanism evoked by cells for defense against oxidative stress caused by serum withdrawal.
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PMID:A novel plasma membrane quinone reductase and NAD(P)H:quinone oxidoreductase 1 are upregulated by serum withdrawal in human promyelocytic HL-60 cells. 1217 Oct 70

NADH dehydrogenase-2 (NDH-2) from Escherichia coli is a membrane-bound flavoprotein linked to the respiratory chain. We have previously shown that this enzyme has cupric reductase activity that is involved in hydroperoxide-induced oxidative stress. In this paper we present spectroscopic evidence that NDH-2 contains thiolate-bound Cu(I) with luminescence properties. Purified NDH-2 exhibits an emission band at 670nm with excitation wavelengths of 280 and 580nm. This emission is quenched by the specific Cu(I) chelator bathocuproine disulfonate, but not by EDTA. The luminescence intensity is sensitive to the enzyme substrates and, thus, the Cu(I)-thiolate chromophore reflects the redox and/or conformational states of the protein. There is one copper atom per polypeptide chain of the purified NDH-2, as determined by atomic absorption spectroscopy. Bioinformatics allowed us to recognize a putative copper-binding site and to predict four structural/functional domains in NDH-2: (I) the FAD-binding domain, (II) the NAD(H)-binding domain, (III) the copper-binding domain, and (IV) the domain of anchorage to the membrane containing two transmembrane helices, at the C-terminus. A NDH-2 topology model, based on the secondary structure prediction, is proposed. This is the first description of a copper-containing NADH dehydrogenase. Comparative sequence analysis allowed us to identify a branch of homologous dehydrogenases that bear a similar metal-binding motif.
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PMID:Evidence for Cu(I)-thiolate ligation and prediction of a putative copper-binding site in the Escherichia coli NADH dehydrogenase-2. 1217 61


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