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)

A photosystem I complex containing the polypeptides PSI-A to PSI-L, light-harvesting complex I and ferredoxin:NADP+ oxidoreductase has been isolated from barley using the non-ionic detergent n-decyl-beta-D-maltopyranoside. The ratio between bound ferredoxin:NADP+ oxidoreductase and P700 is 0.4 +/- 0.2. The complex is highly active in catalyzing light-induced transfer of electrons from plastocyanin to NADP+ at rates of 280 +/- 150 and 1800 +/- 800 mumol NADPH/(mg chl.h), without and in the presence of saturating amounts of exogenously added ferredoxin:NADP+ oxidoreductase, respectively. Endogenously bound ferredoxin:NADP+ oxidoreductase interacts with the PSI-E subunit as demonstrated by cross-linking experiments using two different types of cross-linkers and identification of the products by Western blotting and the use of monospecific antibodies.
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PMID:The PSI-E subunit of photosystem I binds ferredoxin:NADP+ oxidoreductase. 139 6

Recent studies have shown that intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in ethanol or intramural injection of TNBS in saline produces an acute and possibly chronic colitis in rats. It has been assumed that interstitial TNBS initiates the inflammatory response via macrophage-mediated recognition and degradation of TNBS-modified mucosal cells and proteins. However, it is known that certain flavoproteins and/or reductants interact with compounds containing the nitro functional group to generate pro-inflammatory, nitrogen-centered free radicals and reactive oxygen metabolites. The objective of this study was to assess the ability of the rat colon, using either colon homogenates, isolated colonocytes, or intestinal interstitial fluid, to produce reactive oxygen species via enzymatic and/or nonenzymatic metabolism of TNBS. It was found that the addition of TNBS (1 mmol/L) to the 10,000 x g supernatant of rat colon homogenates increased the rate of superoxide production from normally undetectable levels to 2.6 +/- 0.23 nmol.min-1.mg protein-1. Addition of nicotinamide adenine dinucleotide, reduced form (NADH; 1 mmol/L) to colon homogenates containing TNBS significantly enhanced superoxide production to 10.4 +/- 0.9 nmol.min-1.mg-1. Similarly, addition of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH; 1 mmol/L) to colon extracts containing TNBS produced an even further increase in the rate of superoxide formation to 25.2 +/- 1.1 nmol.min-1.mg-1. Addition of NADH or NADPH to the colon homogenate in the absence of TNBS produced no detectable superoxide formation, suggesting that TNBS was required for the enhanced oxidative metabolism. In a separate series of experiments, it was found that isolated colonocytes produced small but significant amounts of superoxide (3.15 +/- 0.6 nmol/2 x 10(6) cells) that were significantly increased in the presence of ethanol to 6.55 +/- 1.14 nmol/2 x 10(6) cells. Using purified preparations of two flavoproteins found in the rat colon, it was shown that the addition of TNBS (1 mmol/L) to purified NADH dehydrogenase or glutathione reductase increased the rate of superoxide formation by these enzymes from normally undetectable levels to 1.6 nmol/min and 1.2 nmol/min, respectively. In addition, it was found that intestinal interstitial fluid (lymph) initiated redox cycling of TNBS such that 28.1 +/- 1.6 nmol of oxygen was consumed per minute per milliliter of lymph. This increase in oxygen consumption was inhibited by the addition of superoxide dismutase and catalase. One possible metabolite involved in both mucosal and lymph-mediated metabolism of TNBS is ascorbic acid.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolism of trinitrobenzene sulfonic acid by the rat colon produces reactive oxygen species. 164 28

Neutrophil myeloperoxidase, hydrogen peroxide, and chloride constitute a potent antimicrobial system with multiple effects on microbial cytoplasmic membranes. Among these is inhibition of succinate-dependent respiration mediated, principally, through inactivation of succinate dehydrogenase. Succinate-dependent respiration is inhibited at rates that correlate with loss of microbial viability, suggesting that loss of respiration might contribute to the microbicidal event. Because respiration in Escherichia coli can be mediated by dehydrogenases other than succinate dehydrogenase, the effects of the myeloperoxidase system on other membrane dehydrogenases were evaluated by histochemical activity stains of electrophoretically separated membrane proteins. Two bands of succinate dehydrogenase activity proved the most susceptible to inactivation with complete loss of staining activity within 20 min, under the conditions employed. A group with intermediate susceptibility, consisting of lactate, malate, glycerol-3-phosphate, and dihydroorotate dehydrogenases as well as three bands of glucose-6-phosphate dehydrogenase, was almost completely inactivated within 30 min. The relatively resistant group, including the dehydrogenases for glutamate, NADH, and NADPH and the remaining bands of glucose-6-phosphate dehydrogenase, retained substantial amounts of diaphorase activity for up to 60 min of incubation with the myeloperoxidase system. The differential effects of myeloperoxidase on dehydrogenase inactivation could not be correlated with published enzyme contents of flavin or iron-sulfur centers, potential targets of myeloperoxidase-derived oxidants. Despite the relative resistance of NADH dehydrogenase/diaphorase activity to myeloperoxidase-mediated inactivation, electron transport particles prepared from E. coli incubated for 20 min with the myeloperoxidase system lost 55% of their NADH oxidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential inactivation of Escherichia coli membrane dehydrogenases by a myeloperoxidase-mediated antimicrobial system. 169 36

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

NADH-ubiquinone reductase of bovine heart submitochondrial particles as prepared is unable to catalyze either the direct or reverse electron transfer from NADH to ubiquinone. The deactivated state of the enzyme in coupled particles was revealed as: (i) the absence of the rotenone-sensitive, delta mu H(+)-dependent succinate-ferricyanide reductase activity; (ii) a prominent lag in the aerobic succinate-supported, delta mu H(+)-dependent NAD+ reduction; and (iii) a lag in the rotenone-sensitive NADH-ubiquinone reductase or NADH oxidase activities. Being inactive as NADH-ubiquinone reductase (direct or reverse), the enzyme is fully active as rotenone-insensitive NADH-ferricyanide reductase. The enzyme can be activated by preincubation with substrates (NADH or NADPH) only under the conditions where the turnover of the NADH-ubiquinone reductase reaction (but not in the NADH-ferricyanide reductase) occurs. Partial activation of the enzyme was observed when the particles were preincubated with rotenone. Neither NADH under the conditions when the ubiquinone pool was reduced nor succinate plus delta mu H+ or dithionite were able to activate the enzyme. Once activated, the enzyme remains in the active state for quite a long time (more than 5 h at 0 degree C). The deactivation rate is extremely temperature-dependent, being insensitive to NAD+, ferricyanide or succinate. A comparison of the enzyme activation/deactivation kinetics showed that the same mechanism is involved in the slow activation of the direct and reverse electron transfer from NADH to ubiquinone. Activated particles catalyze the aerobic delta mu H(+)-dependent succinate-supported reverse electron transfer in the absence of ATP at a rate comparable with that of NADH-ubiquinone reductase.
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PMID:Slow active/inactive transition of the mitochondrial NADH-ubiquinone reductase. 211 5

This study investigates the effects of daunorubicin, 4-demethoxy-daunorubicin, 11-deoxydaunorubicin, 5-imino-daunorubicin, doxorubicin, 4'-epidoxorubicin and the new derivative 4'-iodo-4'-deoxydoxorubicin, on superoxide anion production in heart sarcosomes and by mitochondrial NADH dehydrogenase. In cardiac sarcosomes all the anthracyclines tested enhanced NADPH-dependent superoxide formation which followed Michaelis-Menten kinetics and their Vmax were similar to that of doxorubicin except 5-iminodaunorubicin which did not affect superoxide production and 4'-iodo-4'-deoxydoxorubicin which showed significantly lower Vmax and Km. The superoxide formation by NADH dehydrogenase in the presence of anthracyclines appeared to follow saturation kinetics, depending by NADH. 4-Demethoxydaunorubicin and 4'-epidoxorubicin showed Vmax higher than that of doxorubicin although the Km values were similar. By contrast 5-iminodaunorubicin failed to increase superoxide production over control levels and 4'-Iodo-4'-deoxydoxorubicin hardly enhanced superoxide production by NADH dehydrogenase. A marked difference of superoxide formation rate was shown for the molecules tested in our in vitro system. The behaviour displayed in vitro by the imino- and iodo-derivatives well correlate to their moderate cardiotoxicity in vivo. For the other molecules tested, the poor correlation between the in vitro production of superoxides and the in vivo cardiotoxicity degree might depend on the pharmacokinetic steps which may modify the cardiac effects of these anthracyclines.
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PMID:Superoxide anion production by doxorubicin analogs in heart sarcosomes and by mitochondrial NADH dehydrogenase. 215 33

Several NAD(P)H-dependent ferri-reductase activities were detected in sub-cellular extracts of the yeast Saccharomyces cerevisiae. Some were induced in cells grown under iron-deficient conditions. At least two cytosolic iron-reducing enzymes having different substrate specificities could contribute to iron assimilation in vivo. One enzyme was purified to homogeneity: it is a flavoprotein (FAD) of 40 kDa that uses NADPH as electron donor and Fe(III)-EDTA as artificial electron acceptor. Isolated mitochondria reduced a variety of ferric chelates, probably via an 'external' NADH dehydrogenase, but not the siderophore ferrioxamine B. A plasma membrane-bound ferri-reductase system functioning with NADPH as electron donor and FMN as prosthetic group was purified 100-fold from isolated plasma membranes. This system may be involved in the reductive uptake of iron in vivo.
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PMID:Iron-reductases in the yeast Saccharomyces cerevisiae. 218 97

This is the confirmation of an earlier indication (Mersel, M., Malviya, A.N., Hindelang, C. and Mandel, P. (1984) Biochim. Biophys. Acta 778, 144-154) that the plasma membrane of astrocytes in primary cultures is endowed with DT-diaphorase (EC 1.6.99.2) activity. It is observed that the NADPH-2,6-dichloroindophenol diaphorase activity found in the isolated plasma membrane is not inhibited by dicoumarol. DT-diaphorase-type activity is also observed on the cell surface employing dichloroindophenol as external electron acceptor and it is found to be a dicoumarol-sensitive NADH dehydrogenase.
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PMID:The nature of DT-diaphorase (EC 1.6.99.2) activity in plasma membrane of astrocytes in primary cultures. 242 69

Medium chain length dicarboxylic acids (DA) from C8 to C13 are competitive inhibitors of tyrosinase in vitro. The introduction of electron acceptor groups or electron donor groups into the 2 and/or the 8 position of the molecule enhances or reduces respectively the inhibitory effects of DA. In addition to tyrosinase, DA can reversibly inhibit thioredoxin reductase, NADPH cytochrome P450 reductase, NADH dehydrogenase, succinic dehydrogenase and H2CoQ-Cytochrome C oxidoreductase. Among DA, azelaic acid (AA, C9 dicarboxylic acid) is extensively used because: 1) it is much cheaper than other DA; 2) it has no apparent toxic or teratogenic or mutagenic effect; 3) when administered perorally to humans, at the same concentrations as the other DA, it reaches much higher serum and urinary concentrations. Serum concentrations and urinary excretion obtained with intravenous or intra-arterial infusions of AA are significantly higher than those achievable by oral administration. Together with AA, variable amounts of its catabolites, mainly pimelic acid, are found in serum and urine, indicating an involvement of mitochondrial beta-oxidative enzymes. Short-lived serum levels of AA follow a single 1 h intravenous infusion, but prolonging the period of infusion with successive doses of similar concentration produces sustained higher levels during the period of administration. These levels are consistent with the concentrations of AA capable of producing a cytotoxic effect on tumoral cells in vitro. AA is capable of crossing the blood-brain barrier: its concentration in the cerebrospinal fluid is normally in the range of 2-5% of the values in the serum.
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PMID:Azelaic acid--biochemistry and metabolism. 250 63

The yeast C. parapsilosis CBS7157 is strictly dependent on oxidative metabolism for growth since it lacks a fermentative pathway. It is nevertheless able to grow on high glucose concentrations and also on a glycerol medium supplemented with antimycin A or drugs acting at the level of mitochondrial protein synthesis. Besides its normal respiratory chain C. parapsilosis develops a second electron transfer chain antimycin A-insensitive which allows the oxidation of cytoplasmic NAD(P)H resulting from glycolytic and hexose monophosphate pathways functioning through a route different from the NADH-coenzyme Q oxidoreductase described in S. cerevisiae or from the alternative pathways described in numerous plants and microorganisms. The second respiratory chain of C. parapsilosis involves 2 dehydrogenases specific for NADH and NADPH respectively, which are amytal and mersalyl sensitive and located on the outer face of the inner membrane. Since this antimycin A-insensitive pathway is fully inhibited by myxothiazol, it was hypothesized that electrons are transferred to a quinone pool that is different from the classical coenzyme Q-cytochrome b cycle. Two inhibitory sites were evidenced with myxothiazol, one related to the classical pathway, the other to the second pathway and thus, the second quinone pool could bind to a Q-binding protein at a specific site. Elimination of this second pool leads to a fully antimycin A-sensitive NADH oxidation, whereas its reincorporation in mitochondria allows recovery of an antimycin A-insensitive, myxothiazol sensitive NADH oxidation. The third step in this second respiratory chain involves a specific pool of cytochrome c which can deliver electrons either to a third phosphorylation site or to an alternative oxidase, cytochrome 590. This cytochrome is inhibited by high cyanide concentrations and salicylhydroxamates.
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PMID:The second respiratory chain of Candida parapsilosis: a comprehensive study. 250 62


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