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:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Treatment of submitochondrial particles (ETP) with trypsin at 0 degrees destroyed NADPH leads to NAD (or 3-acetylpyridine adenine dinucleotide, AcPyAD) transhydrogenase activity. NADH oxidase activity was unaffected; NADPH oxidase and NADH leads to AcPyAD transhydrogenase activities were diminished by less than 10%. When ETP was incubated with trypsin at 30 degrees, NADPH leads to NAD transhydrogenase activity was rapidly lost, NADPH oxidase activity was slowly destroyed, but NADH oxidase activity remained intact. The reduction pattern by NADPH, NADPH + NAD, and NADH of chromophores absorbing at 475 minus 510 nm (flavin and iron-sulfur centers) in complex I (NADH-ubiquinone reductase) or ETP treated with trypsin at 0 degrees also indicated specific destruction of transhydrogenase activity. The sensitivity of the NADPH leads to NAD transhydrogenase reaction to trypsin suggested the involvement of susceptible arginyl residues in the enzyme. Arginyl residues are considered to be positively charged binding sites for anionic substrates and ligands in many enzymes. Treatment of ETP with the specific arginine-binding reagent, butanedione, inhibited transhydrogenation from NADPH leads to NAD (or AcPyAD). It had no effect on NADH oxidation, and inhibited NADPH oxidation and NADH leads to AcPyAD transhydrogenation by only 10 to 15% even after 30 to 60 min incubation of ETP with butanedione. The inhibition of NADPH leads to NAD transhydrogenation was diminished considerably when butanedione was added to ETP in the presence of NAD or NADP. When both NAD and NADP were present, the butanedione effect was completely abolished, thus suggesting the possible presence of arginyl residues at the nucleotide binding site of the NADPH leads to NAD transhydrogenase enzyme. Under conditions that transhydrogenation from NADPH to NAD was completely inhibited by trypsin or butanedione, NADPH oxidation rate was larger than or equal to 220 nmol min-1 mg-1 ETP protein at pH 6.0 and 30 degrees. The above results establish that in the respiratory chain of beef-heart mitochondria NADH oxidation, NADPH oxidation, and NADPH leads to NAD transhydrogenation are independent reactions.
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PMID:Oxidation of NADPH by submitochondrial particles from beef heart in complete absence of transhydrogenase activity from NADPH to NAD. 0 Mar 95

The soluble NADH dehydrogenase of low molecular weight, isolated from complex I (NADH:ubiquinone oxidoreductase, EC 1.6.5.3) of the respiratory chain, has been shown to have NADPH dehydrogenase and NADPH leads to NAD transhydrogenase activities. Both activities are greatly increased in the presence of added guanidine-HCl and at pH values less than 6.5. The chromophores of the soluble enzyme (flavin and iron--sulfur centers) are reduced by NADH and NADPH to the same extent. The latter reduction is extremely slow, and is considerably stimulated in the presence of guanidine-HCl. The soluble dehydrogenase has little or no NADH leads to NADP and NADPH leads to NADP transhydrogenase activity. The former reaction is known to be energy-linked in submitochondrial particles; the latter was shown in the present studies also to be energy-linked. In view of the above and earlier results, possible mechanisms for dehydrogenation and transhydrogenation (nonenergy-linked and energy-linked) involving reduced and oxidized NAD and NADP are proposed.
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PMID:Dehydrogenase and transhydrogenase properties of the soluble NADH dehydrogenase of bovine heart mitochondria. 1 55

In the subcommissural organ (SCO) of the guinea pig, rat, golden hamster, and mouse the activity and distribution of enzymes related to the energy-supplying metabolism and of some marker enzymes of different cell organelles have been investigated by means of mostly modified histochemical methods. The results were compared with findings in the ciliated ependyma of the ventricular wall and with those in the ependyma of the choroid plexus of the third ventricle. In the ependymal part of the SCO only a moderate activity of hexokinase is observed in its specialized columnar cells whereas a high activity is present both in the ciliated ependyma and the choroid plexus. - The staining pattern of glucose-6-phosphatase is similar to that of hexokinase but this enzyme is found is the SCO only. - Likewise hexokinase, glycogen granules and enzymes related to glycogen metabolism (phosphoglucomutase, uridine-diphosphoglucose pyrophosphorylase, glycogen synthetase and phosphorylase) are regularly found most numerous and active in the nuclear and supra-nuclear area of the ependymal part. These enzymes are less active in both the other ependymal regions. - Uridine-diphosphoglucose dehydrogenase could not be demonstrated in the SCO. The NADP-linked enzymes of the pentose phosphate shunt, glucose-6-phosphate and 6-phosphogluconate dehydrogenase, show a moderate activity which decreases also from the nuclear towards the apical area of the ependymal cells of the SCO. Enzymes of the glycolytic pathway, such as glucosephosphate isomerase, fructose-6-phosphate kinase, fructose-I,6-diphosphate aldolase, glyceraldehyde-3-phosphate and lactate dehydrogenase, are highly active in the SCO and are located mainly in the supranuclear area, too. Fructose-1,6-diphosphatase could not be demonstrated thus indicating that in the SCO the pathway is most probably only glycolytic but not gluconeogenetic. Compared to the ependyma of the ventricular wall and of the choroid plexus, in the SCO the M type subunits of lactate dehydrogenase predominate. Glycolytic enzymes are also very active in the choroid plexus but less in the ciliated ependyma. Compared to the ciliated ependyma and especially to the ependyma of the choroid plexus, the activities of enzymes which are only present in mitochondria (NAD-linked isocitrate dehydrogenase, succinate dehydrogenase, NAD-linked malate dehydrogenase after preextraction, cytochrome oxidase, 3-hydroxybutyrate and glycerolphosphate and glutamate dehydrogenase) are relatively low. Mitochondria are accumulated near the superior pole of the nuclei as well as in the most apical part of the ependymal cells. - The staining pattern of NADP-linked isocitrate and malate dehydrogenase as well as of NADH dehydrogenase suggests that these enzymes are localized both in and out of mitochondria. The extramitochondrial activity of the first two enzymes might be localized in the cytosol. The extramitochondrial activity of NADH dehydrogenase might be localized in the endoplasmic reticulum...
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PMID:Enzymatic organization of the subcommissural organ. 123 49

Both the external oxidation of NADH and NADPH in intact potato (Solanum tuberosum L. cv. Bintje) tuber mitochondria and the rotenone-insensitive internal oxidation of NADPH by inside-out submitochondrial particles were dependent on Ca2+. The stimulation was not due to increased permeability of the inner mitochondrial membrane. Neither the membrane potential nor the latencies of NAD(+)-dependent and NADP(+)-dependent malate dehydrogenases were affected by the addition of Ca2+. The pH dependence and kinetics of Ca(2+)-dependent NADPH oxidation by inside-out submitochondrial particles were studied using three different electron acceptors: O2, duroquinone and ferricyanide. Ca2+ increased the activity with all acceptors with a maximum at neutral pH and an additional minor peak at pH 5.8 with O2 and duroquinone. Without Ca2+, the activity was maximal around pH 6. The Km for NADPH was decreased fourfold with ferricyanide and duroquinone, and twofold with O2 as acceptor, upon addition of Ca2+. The Vmax was not changed with ferricyanide as acceptor, but increased twofold with both duroquinone and O2. Half-maximal stimulation of the NADPH oxidation was found at 3 microM free Ca2+ with both O2 and duroquinone as acceptors. This is the first report of a membrane-bound enzyme inside the inner mitochondrial membrane which is directly dependent on micromolar concentrations of Ca2+. Mersalyl and dicumarol, two potent inhibitors of the external NADH dehydrogenase in plant mitochondria, were found to inhibit internal rotenone-insensitive NAD(P)H oxidation, at the same concentrations and in manners very similar to their effects on the external NAD(P)H oxidation.
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PMID:Effect of calcium ions and inhibitors on internal NAD(P)H dehydrogenases in plant mitochondria. 172 51

The NADH dehydrogenase complex isolated from Paracoccus denitrificans is composed of approximately 10 unlike polypeptides and contains noncovalently bound FMN, non-heme iron, and acid-labile sulfide [Yagi, T. (1986) Arch. Biochem. Biophys. 250, 302-311]. When the Paracoccus NADH dehydrogenase complex was irradiated by UV light in the presence of [adenylate-32P]NAD, radioactivity was incorporated exclusively into one of three polypeptides of Mr approximately 50,000. Similar results were obtained when [adenylate-32P]NADH was used. The labeling of the Mr 50,000 polypeptide was diminished when UV irradiation of the enzyme with [adenylate-32P]NAD was performed in the presence of NADH, but not in the presence of NADP(H). The labeled polypeptide was isolated by preparative sodium dodecyl sulfate gel electrophoresis and was shown to cross-react with antiserum to the NADH-binding subunit (Mr = 51,000) of bovine NADH-ubiquinone oxidoreductase. Its amino acid composition was also very similar to that of the bovine NADH-binding subunit. These chemical and immunological results indicate that the Mr 50,000 polypeptide is an NADH-binding subunit of the Paracoccus NADH dehydrogenase complex.
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PMID:Identification of the NADH-binding subunit of NADH-ubiquinone oxidoreductase of Paracoccus denitrificans. 211 69

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

Superoxide anion can modulate vascular smooth muscle tone and potentially affect the growth response in vascular disease. The present studies were undertaken to characterize the source of superoxide in rabbit aorta. Rings of aorta (5 mm) were incubated in physiological salt solution (PSS) for 30 min at 37 degrees C in the presence of 10 mM diethyldithiocarbamate (DDC) with or without inhibitors of superoxide-generating systems. Rings were then placed in PSS containing 250 microM lucigenin at 37 degrees C in the presence or absence of inhibitors, and changes in amounts of superoxide were determined by measuring chemiluminescence (units). The inhibitors of xanthine oxidase, oxypurinol (300 microM), and of mitochondrial NADH dehydrogenase, rotenone (50 microM), had no significant effect on superoxide levels. An inhibitor of NADPH oxidase, iodonium thiophen, caused a concentration-dependent inhibition of superoxide anion (12.49 +/- 1.48 vs 5.27 +/- 1.81 and 2.30 +/- 0.36 units, control vs 7 microM and 70 microM iodonium thiopen, respectively). A structurally related iodonium compound, diphenyleneiodonium (20 microM), caused a 78% reduction in basal and DDC-evoked superoxide levels. In the presence or absence of DDC, exogenous administration of NADPH (10 microM-1 mM), but not NADP (1 mM), elicited a concentration-dependent rise in superoxide levels that was inhibited by iodonium thiophen. Particulate fractions of whole aortic tissue exhibited NADPH-dependent superoxide production that was inhibited by 1 microM diphenyleneiodonium.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:An NADPH oxidase superoxide-generating system in the rabbit aorta. 761 77

Bovine leukemia virus-transformed lamb embryo fibroblasts (line FLK) possess activity of DT-diaphorase of ca. 260 U/mg protein and similar levels of other NADP(H)-oxidizing enzymes: NADH:oxidase, 359 U/mg; NADPH:oxidase, 43 U/mg; NADH:cytochrome-c reductase, 141 U/mg; NADPH:cytochrome-c reductase, 43 U/mg. In general, the toxicity of aromatic nitrocompounds towards FLK cells increases on increase of single-electron reduction potentials (E1(1)) of nitrocompounds or the log of their reduction rate constants by single-electron-transferring enzymes, microsomal NADPH:cytochrome P-450 reductase (EC 1.6.2.4) and mitochondrial NADH:ubiquinone reductase (EC 1.6.99.3). No correlation between the toxicity and reduction rate of nitrocompounds by rat liver DT-diaphorase (EC 1.6.99.2) was observed. The toxicity is not significantly affected by dicumarol, an inhibitor of DT-diaphorase. Nitrocompounds examined were poor substrates for DT-diaphorase, being 10(4) times less active than menadione. Their poor reactivity is most probably determined by their preferential binding to a NADPH binding site, but not to menadione binding site of diaphorase. These data indicate that at comparable activities of DT-diaphorase and single-electron-transferring NAD(P)H dehydrogenases in the cell, the toxicity of nitrocompounds will be determined mainly by their single-electron reduction reactions.
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PMID:The toxicity of aromatic nitrocompounds to bovine leukemia virus-transformed fibroblasts: the role of single-electron reduction. 766 3

A genomic DNA fragment from Desulfovibrio fructosovorans, which strongly hybridized with the hydAB genes from Desulfovibrio vulgaris Hildenborough, was cloned and sequenced. This fragment was found to contain four genes, named hndA, hndB, hndC, and hndD. Analysis of the sequence homologies indicated that HndA shows 29, 21, and 26% identity with the 24-kDa subunit from Bos taurus complex I, the 25-kDa subunit from Paracoccus denitrificans NADH dehydrogenase type I, and the N-terminal domain of HoxF subunit of the NAD-reducing hydrogenase from Alcaligenes eutrophus, respectively. HndB does not show any significant homology with any known protein. HndC shows 37 and 33% identity with the C-terminal domain of HoxF and the 51-kDa subunit from B. taurus complex I, respectively, and has the requisite structural features to be able to bind one flavin mononucleotide, one NAD, and three [4Fe-4S] clusters. HndD has 40, 42, and 48% identity with hydrogenase I from Clostridium pasteurianum and HydC and HydA from D. vulgaris Hildenborough, respectively. The 4.5-kb length of the transcripts expressed in D. fructosovorans and in Escherichia coli (pSS13) indicated that all four genes were present on the same transcription unit. The sizes of the four polypeptides were measured by performing heterologous expression of hndABCD in E. coli, using the T7 promoter/polymerase system. The products of hndA, hndB, hndC, and hndD were 18.8, 13.8, 52, and 63.4 kDa, respectively. One hndC deletion mutant, called SM3, was constructed by performing marker exchange mutagenesis. Immunoblotting studies carried out on cell extracts from D. fructosovorans wild-type and SM3 strains, using antibodies directed against HndC, indicated that the 52-kDa protein was recognized in extracts from the wild-type strain only. In soluble extracts from D. fructosovorans wild type, a 10-fold induction of NADP reduction was observed when H(2) was present, but no H(2)-dependent NAD reduction ever occurred. This H(2)-dependent NADP reductase activity disappeared completely in extracts from SM3. These results indicate that the hnd operon actually encodes an NAdP-reducing hydrogenase in D. fructosovorans.
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PMID:Characterization of an operon encoding an NADP-reducing hydrogenase in Desulfovibrio fructosovorans. 775 Dec 70

Epimastigotes of Trypanosoma cruzi, the causative agent of Chagas disease, catabolize proteins and amino acids with production of MH3, and glucose with production of reduced catabolites, chiefly succinate and L-alanine, even under aerobic conditions. This "aerobic fermentation of glucose" is probably due to both the presence of low levels of some cytochromes, causing a relative inefficiency of the respiratory chain for NADH, reoxidation during active glucose catabolism, and the lack of NADH dehydrogenase and phosphorylation site I, resulting in the entry of reduction equivalents into the chain mostly as succinate. Phosphoenol pyruvate carboxykinase and pyruvate kinase may play an essential role in diverting glucose carbon to succinate or L-alanine, and L-malate seems to be the major metabolite for the transport of glucose carbon and reduction equivalents between glycosome and mitochondrion. The parasite contains proteinase and peptidase activities. The major lysosomal cysteine proteinase, cruzipain, has been characterized in considerable detail, and might be involved in the host/parasite relationship, in addition to its obvious role in parasite nutrition. Among the enzymes of amino acid catabolism, two glutamate dehydrogenases (one NADP- and the other NAD-linked), alanine aminotransferase, and the major enzymes of aromatic amino acid catabolism (tyrosine aminotransferase and aromatic alpha-hydroxy acid dehydrogenase), have been characterized and proposed to be involved in the reoxidation of glycolytic NADH.
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PMID:Intermediate metabolism in Trypanosoma cruzi. 805 82


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