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)

1. Whole cells of Methylomonas Pl1 contained ubiquinone, identified as ubiquinone-8. No naphthaquinone was detected. Ubiquinone was located predominantly in the particulate fraction, which also contained most of the NADH oxidase activity. 2. Aerobic incubation of cells with formaldehyde or methanol resulted in about 20% reduction of ubiquinone, irrespective of the presence or absence of dinitrophenol. On inhibition of the respiration by cyanide, ubiquinone became partly reduced by endogenous substrates (15--25%), and a further reduction occurred only in the presence of formaldehyde (up to 60%). When endogenous substrates were completely exhausted, then 44 and 23% of ubiquinone was reduced by formaldehyde or methanol respectively. 3. The difference spectra at room and liquid-N2 temperatures revealed the presence of cytochrome b and two cytochromes c (c-552.5 and c-549) all tightly bound to the membrane. Cytochrome c-552.5 was also found in the soluble fraction. 4. Redox changes of cytochromes b and c, with methanol or formaldehyde as substrates, respond to the aerobic and anaerobic states of the cell and to KCN inhibition in a manner characteristic of the electron carriers of the respiratory chain. 5. The merging point for electron transport from NADH dehydrogenase and formaldehyde dehydrogenase is suggested to be at the level of ubiquinone.
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PMID:The respiratory chain of a newly isolated Methylomonas Pl1. 41 43

The actions of Dexon on the NADH-ferricyanide oxidoreductase and the NADPH oxidase system of electron transfer particles (ETP) from beef heart as well as on the NADPH-cytochrome c oxidoreductase from brewer's yeast (Saccharomyces carlsbergensis Hansen) were investigated. The inhibition of the NADH dehydrogenase activity of ETP and that of the yeast enzyme correspond with respect to the following characteristics: 1) increase in the inhibition, 2) enhancement of the Dexon sensitivity by one order of magnitude after preincubation in the presence of NAD(P)H, 3) irreversibility of the inhibition, 4) no detectable changes in the spectral properties and in coenzyme activity of FMN after acid extraction from Dexon-treated enzyme. The inhibition of the NADH dehydrogenase activity of ETP is diminished by both NAD+ and FMN. However, no interaction of Dexon with NAD(P)H or FMN could be detected in the absence of enzyme or apoenzyme. The concentration of half-inhibition by Dexon for the yeast enzyme corresponds with its FMN concentration. It is proposed that both apoenzyme, NAD(P)H and FMN are involved in the interaction with Dexon. Possible mechanisms of binding are both complanar complexations of the ring systems and a triazene formation between FMNH2 and Dexon. The NADPH oxidase activity of the ETP is partly inhibited; the share inhibited by Dexon may represent the pathway via the transhydrogenase reaction.
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PMID:[Mechanism of action of the inhibition of pyridine-nucleotide-dependent flavine enzymes using the systemic fungicide Dexon]. 41 38

The plasma membrane of the Ehrlich ascites tumor cell contains an NADH dehydrogenase. This activity was shown not to be due to contamination by other subcellular membranes. A variety of electron acceptors have been compared as to rate with the following result: ferricyanide greater than cytochrome c greater than cytochrome b5 greater than glyoxylate greater than dichlorophenolindophenol. Oxygen acceptance could not be detected. The optimum assay temperature and pH ranges were 30--40 degrees C and pH 6--8, respectively. With respect to either NADH or ferricyanide, the kinetics yielded linear double-reciprocal plots. Inhibition of the enzyme by sulfhydryl reagents could be blocked by excess NADH. Detergents such as Triton X-100 or cholate resulted in solubilization of the enzymatic activity, but phospholipase A2 did not. The activity differed from that of the mitochondria in that it was not inhibited by rotenone or antimycin A. The possible involvement of NADH oxidation in the energetics of plasma membrane transport is discussed.
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PMID:Electron-transferring enzymes in the plasma membrane of the Ehrlich ascites tumor cell. 42 30

Formate dehydrogenase, NADH dehydrogenase, a quinone and a b-type cytochrome characterized by maxima at 429 and 560 nm are shown to participate in the tetrathionate redox chain of Citrobacter.
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PMID:Participation of quinone and cytochrome b in tetrathionate reductase respiratory chain of Citrobacter freundii. 43 81

The integral protein of cytochrome b556 after its solubilization with Triton X-100 from M. lysodeikticus membranes was studied. The cytochrome was found in complexes differing in charge and size during preparative gel electrophoresis and centrifugation in a sucrose concentration gradient. Cytochrome b556, being in complexes, retains its ability to be reduced by NADH dehydrogenase. The electron micrographs of the membranes after solubilization by Triton X-100 demonstrated the maintenance of the membrane structure. It is concluded that native protein complexes marked with cytochrome b556 are extracted from the membranes under their solubilization.
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PMID:[Cytochrome b556 complexes solubilized from Micrococcus lysodeikticus membranes by triton X-100]. 43 82

NADH dehydrogenase was isolated from M. lysodeikticus membranes with FAD as a prosthetic group. It was found the enzyme molecular weight is about 140000 in 0,01 M phosphate buffer, pH 7,4 in 1% Triton X-100. The enzyme molecules are dimers consisting of two subunits with molecular weight of 70000. The content of alpha-helical regions is 30%, that of beta-forms is 13%. The protein globule is cross-linked with the disulfide bonds and has hydrophobic regions on its surface.
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PMID:[Bacterial membrane proteins. Properties of Micrococcus lysodeikticus NADH dehydrogenase]. 45 11

The site of Na+-dependent activation in the respiratory chain of the marine bacterium, Vibrio alginolyticus, was investigated. The respiratory chain system contained ubiquinones (Q), menaquinones (MK), cytochromes b(560), c(553), d(630), and o(560). The membrane-bound and partially purified NADH dehydrogenase was stimulated 2- to 3-fold by the addition of 0.2 M Na+ or K+ and no specific requirement for Na+ was observed in this reaction step. The cytochrome oxidase showed no requirement for monovalent cations. The respiratory activity (NADH oxidase) of the membrane was lost on removal of the quinones, and the reincorporation of authentic Q-10 or MK-4 restored the activity. The rate of MK-4 reduction by NADH (menaquinone reductase) as measured using MK-4 incorporated membrane was activated by Na+, but only slightly by K+. The apparent Ka for Na+ was 78 mM for both menaguinone reductase and NADH oxidase. The requirement for Na+ of menaquinone reductase was greatly reduced in the presence of 0.2 M K+. Ubiquinone reductase as measured by using Q-10 incorporated membrane was also activated more effectively by Na+ than by K+. These results strongly suggested that the site of Na+-dependent activation in the respiratory chain of marine V. alginolyticus was at the step of NADH; quinone oxidoreductase.
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PMID:NADH: quinone oxidoreductase as a site of Na+-dependent activation in the respiratory chain of marine Vibrio alginolyticus. 45 42

Cells of Rhodopseudomonas capsulata, strain 37b4, leu-, precultivated anaerobically under low light intensity, were exposed to high light intensity (2000 W.m-2). The cells grew with a mass doubling time of 3 h. The synthesis of bacteriochlorophyll (BChl) began after two doublings of cell mass. Reaction center and light-harvesting BChl I (B-875) were the main constituents of the photosynthetic apparatus incorporated into the membrane. The size of the photosynthetic unit (total BChl/reaction center) decreased and light-harvesting BChl I became the dominating BChl species. Concomitant with the appearance of the different spectral forms of BChl the respective proteins were incorporated into the membrane, i.e. the three reaction center polypeptides, the polypeptide associated with light-harvesting BChl I, the two polypeptides associated with BChl II. A polypeptide of an apparent molecular weight of 45 000 was also incorporated. A lowering of the light intensity to 7 W.m-2 resulted in a lag phase of growth for 6 h. Afterwards, the time for doubling of cell mass was 11 h. The concentration of all three BChl complexes (reaction center, light-harvesting BChl I and II complexes)/cell and per membrane protein increased immediately. Also the size of the photosynthetic unit and the amount of intracytoplasmic membranes/cell increased. The activities of photophosphorylation, succinate dehydrogenase, NADH dehydrogenase and NADH oxidation (respiratory chain)/membrane protein are higher in membrane preparations isolated from cells grown at high light intensities than in such preparations from cells grown at low light intensities.
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PMID:Effects of light intensity on membrane differentiation in Rhodopseudomonas capsulata. 48 32

1. Previous studies have established that diphenyleneiodonium binds to and inhibits the respiratory enzyme NADH dehydrogenase and also catalyses an exchange of Cl- for OH- across membranes. 2. The hypoglycaemia produced by diphenyleneiodonium was confirmed and shown to be reversible at a dose of 4 mg/kg in starved rats. 3. The lethality of diphenyleneiodonium in mice was cumulative. 4. Presumably as a result of the Cl-/OH- exchange, diphenyleneiodonium-treated rats excreted less Cl- than controls in the first 12 h after administration. However, the swelling of erythrocytes observed in vitro did not occur in vivo. 5. When [125I]diphenyleneiodonium was administered to rats and rabbits, its distribution did not appear to be governed by its binding to NADH dehydrogenase. Reasons for this are discussed. 6 Over 90% of the radioactivity excreted in the faeces of rabbits could not be extracted with boiling water or with dil. HNO3.
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PMID:Some aspects of the pharmacology of diphenyleneiodonium, a bivalent iodine compound. 52 14

Spectrophotometric and fluorimetric substrate couple titrations and potentiometric spectrophotometric titrations were used to determine the oxidation-reduction potentials of components showing absorbance or fluorescence at the wavelengths attributable to the flavoproteins of mitochondria fractionated using digitonin together with sonication. A pure mitoplast fraction devoid of cytochrome b5 contamination could be obtained using 230 micrograms digitonin/mg of mitochondrial protein. The digitonin-soluble fraction contained a species having Em7.4 = -123 mV and probably represents the outer membrane flavoproteins. The inner membrane-matrix fraction, treated with ultrasound, provided evidence of a flavoprotein species with redox potential (Em7.4 = -302 mV) in the matrix fraction. The -302 mV component is probably lipoamide dehydrogenase. A high redox potential species with Em7.4 = +19 mV in titrations with the succinate fumarate couple was located in the inner membrane vesicles and is probably identical with succinate dehydrogenase. The electron-transferring flavoprotein (ETF) was isolated from bovine heart mitochondria and its Em7.4 = -74 mV determined. The component in the matrix fraction with an apparent Em7.4 = -56 mV probably represents ETF, and that in the inner membrane fraction with an apparent Em7.4 = -43 mV the NADH dehydrogenase flavoprotein. A component in an apparently low concentration with Em7.4 = +30 mV was detected in the inner membrane fraction. This probably represents the ETF-dehydrogenase flavoprotein. The origin of the flavoprotein fluorescence of mitochondria and intact tissues is discussed.
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PMID:Oxidation-reduction midpoint potentials of mitochondrial flavoproteins and their intramitochondrial localization. 55 61


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