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)

1. The midpoint potentials of the various iron-sulphur centres in Site I were determined at different pH values by the technique of redox potentiometry. An interesting feature is the pH-dependence of Centre N-2, the highest potential component of the NADH dehydrogenase segment of the respiratory chain. 2. The apparent midpoint potentials of Centre N-2 (NADH dehydrogenase) and S-1 (succinate dehydrogenase) and their pH-dependence was also determined by using the succinate/fumarate couple. Again Centre N-2 is pH-dependent in midpoint potential, and Centre S-1 is not. The results obtained by titrating with the succinate/fumarate couple are in quantitative agreement with those obtained for these centres by redox potentiometry. 3. Oxidation-reduction titrations of iron-sulphur centres with the couple NADH/NAD+ and an analogue APADH/APAD+ in the presence of rotenone gave results substantially different from those obtained by redox potentiometry; these differences may be due to the mechanism of action of NADH dehydrogenase and its specific interaction with NADH. 5. The addition of ATP to an NAD+/NADH-poised system induces an uncoupler-sensitive oxidation of Centre N-4.
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PMID:An analysis of some thermodynamic properties of iron-sulphur centres in site I of mitochondria. 624 37

The effect of p-toluyl m-nitro-piperazine on energy conservation processes in rat liver mitochondria is presented. The drug showed an inhibitory effect on the three segments of the respiratory chain and on the ATPase system. NADH oxidase and NADH dehydrogenase activity was inhibited 100%. The velocity and amplitude of swelling induced by glutamate, succinate, ascorbate + TMPD, and ATP was significantly changed by p-toluyl m-nitro-piperazine. It was suggested that the general action of the drug on mitochondrial metabolism would be concerning with modifications on mitochondrial membrane.
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PMID:Possible mechanism of action of piperazine derivatives on liver mitochondria. I--Effect of p-toluyl m-nitro-piperazine (p-TNP). 627 80

1. Plasma membranes were isolated from Krebs II ascite cells grown in the mouse. Cells were disrupted by nitrogen cavitation in an isotonic alkaline buffer containing magnesium and ATP. Isolation was performed in an alkaline-buffered self-generating gradient of Percoll with an angular rotor. At each step of the preparation, the pH appeared as the critical aspect of our procedure. 2. External membrane markers were concanavalin A and 5'-nucleotidase (EC 3.1.3.5). They reached a relative specific activity of 10, whereas this value was only of 0.7 for the endoplasmic reticulum marker, NADH dehydrogenase (EC 1.6.99.3). 3. Plasma membrane from 4 ml packed cells were isolated within 1 h after homogenization with good yield: 50% and 67% of total [3H]concanavalin A and 5'-nucleotidase, respectively, were recovered in the two plasma membrane fractions. 4. Electron microscopy examination showed the presence of vesicles of different sizes devoid of other structural contaminants. 5. Using the specific binding of concanavalin A to the external cell membrane, it was calculated that about 50% of the total cell phospholipid and 10% protein are located in the plasma membrane. Their sphingomyelin content is much higher than in the whole cell, in contrast to phosphatidylinositol, known as a more specific endoplasmic reticulum phospholipid.
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PMID:Isolation and characterization of plasma membranes from krebs II ascite cells using Percoll gradient. 628 35

The reduction and the potential autoxidation of quinoid compounds may be viewed as taking place in three cell compartments. In microsomal fractions (endoplasmic reticulum) one-electron reduction by NAPDH-cytochrome P450 reductase leads to the formation of semiquinones which rapidly react with oxygen to form the parent quinone and superoxide anions. The formation of superoxide through this futile cycle leads ultimately to other damaging species (H2O2 and .OH). A similar futile cycle in mitochondria involves NADH dehydrogenase. In this instance, mitochondria initiation of such a cycle with quinones results not only in the formation of toxic radical species but also in the diversion of electrons from phosphorylating pathways. The consequent diminution of cellular ATP may have as important a consequence with respect to the toxicity of quinones as the generation of radicals. Finally, cytosolic DT diaphorase, which carries out a two-electron reduction of quinones to more stable hydroquinones, may compete with the one-electron systems and participate in the detoxification of quinones by supplying hydroquinones for conjugation reactions. The extent of quinone-induced damage may thus vary from cell to cell depending on the integration of these pathways.
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PMID:Futile redox cycling: implications for oxygen radical toxicity. 631 61

The structural and kinetic parameters of the oxidative phosphorylation system responsible for synchronization of the respiratory chain and ATP-synthetase function in mitochondria were studied. It was shown that regulation of ATP-synthetase function by the respiratory chain can be realized only within the whole ATP-synthetase complex (F0F1). NADH dehydrogenase and succinate dehydrogenase doe not control synchronization of ATP-synthetase function in the mitochondria. Data from the inhibitory analysis suggest that the ATP-synthetase function depends on the rate of the enzyme operation but not on the redox state of the respiratory chain carriers.
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PMID:[Structural and kinetic parameters of the oxidative phosphorylation system, participating in the synchronization of mitochondrial respiratory chain and ATP-synthetase functions]. 632 63

Erythrocyte ghost NADH dehydrogenase is inhibited in a competitive fashion by ATP and ADP whereas other nucleoside di- and triphosphates, cyclic nucleosides, as well as non-phosphorylating ATP analogs are relatively ineffective. In addition, this enzyme, measured with ferricyanide as electron acceptor, is inhibited by uncouplers of oxidative phosphorylation (proton-conducting reagents), the inhibition being competitive in character (i.e., the uncouplers were without influence upon maximum velocity). The effectiveness of the uncouplers was in the order of their hydrophobic character with the presence of the alkyl side chain rendering nonyl-dinitrophenol much more active than 2,6-dinitrophenol itself. Hydrophobic compounds that are not protonophores (e.g., eosin, proflavin or valinomycin) were not inhibitory. Whereas adenine nucleotides probably inhibit NADH oxidation competitively through structural similarity with the substrate, it appears unlikely that uncouplers compete at the NADH site directly. Rather, the apparently-competitive inhibition in the latter case may reflect competition for proton transfer to an acceptor residing in a hydrophobic region of the enzyme complex.
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PMID:Inhibition of erythrocyte plasma membrane NADH dehydrogenase by nucleotides and uncouplers. 650 43

TMB-8 inhibited respiration of rat thymocytes and rat liver mitochondria, probably by inhibition of NADH dehydrogenase. TMB-8 markedly decreased both the cellular ATP concentration and the mitochondrial membrane potential in situ in thymocytes. These effects occurred at, or well below, the concentrations used in other systems to investigate the role of intracellular calcium pools in signalling events. We conclude that caution should be exercised in the interpretation of the effects of TMB-8.
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PMID:The intracellular calcium antagonist TMB-8 [8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate] inhibits mitochondrial ATP production in rat thymocytes. 652 71

NADH dehydrogenase from Bacillus subtilis W23 has been isolated from membrane vesicles solubilized with 0.1% Triton X-100 by hydrophobic interaction chromatography on an octyl-Sepharose CL-4B column. A 70-fold purification is achieved. No other components could be detected with sodium dodecyl sulphate polyacrylamide gel electrophoresis. Ferguson plots of the purified protein indicated no anomalous binding of sodium dodecyl sulphate and an accurate molecular weight of 63 000 could be determined. From the amino acid composition a polarity of 43.8% was calculated indicating that the protein is not very hydrophobic. Optical absorption spectra and acid extraction of the enzyme chromophore followed by thin-layer chromatography showed that the enzyme contains 1 molecule FAD/molecule. The enzyme was found to be specific for NADH. NADPH is oxidized at a rate which is less than 6% of the rate of NADH oxidation. The activity of the enzyme as determined by NADH:3-(4'-5'-dimethyl-thiazol-2-yl)2,4-diphenyltetrazolium bromide oxidoreduction is optimal at 37 C and pH 7.5-8.0. The purified enzyme has a Kapp for NADH of 60 microM and a V of 23.5 mumol NADH/min X mg protein. These parameters are not influenced by phospholipids. The enzyme activity is hardly or not at all affected by NADH-related compounds such as ATP, ADP, AMP, adenosine, deoxyadenosine, adenine and nicotinic amide indicating the high binding specificity of the enzyme for NADH.
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PMID:Purification and characterization of NADH dehydrogenase from Bacillus subtilis. 681 92

Exogenous NAD+ stimulated the rotenone-resistant oxidation of all the NAD+-linked tricarboxylic acid-cycle substrates in mitochondria from Jerusalem artichoke (Helianthus tuberosus L.) tubers. The stimulation was not removed by the addition of EGTA, which is known to inhibit the oxidation of exogenous NADH. It is therefore concluded that added NAD+ gains access to the matrix space and stimulates oxidation by the rotenone-resistant NADH dehydrogenase located on the matrix surface of the inner membrane. Added NAD+ stimulated the activity of malic enzyme and displaced the equilibrium of malate dehydrogenase; both observations are consistent with entry of NAD+ into the matrix space. Analysis of products of malate oxidation showed that rotenone-resistant oxygen uptake only occurred when the concentration of oxaloacetate was low and that of NADH was high. Thus it is proposed that the concentration of NADH regulates the activity of the two internal NADH dehydrogenases. Evidence is presented to suggest that the rotenone-resistant NADH dehydrogenase is engaged under conditions of high phosphorylation potential, which restricts electron flux through the rotenone-sensitive dehydrogenase (coupled to ATP synthesis).
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PMID:Regulation of malate oxidation in plant mitochondria. Response to rotenone and exogenous NAD+. 681 64

A soluble NADH dehydrogenase (NADH:ferricyanide oxidoreductase) has been obtained by simple disruption of cells of Thermus aquaticus strain T351, and purified. The enzyme is of low molecular mass, 50 000 Da, and displays many of the properties of the membrane-bound enzyme, including inhibition by both NADH and ferricyanide, and the same Km for ferricyanide. The enzyme contains 0.05 mol of FMN, 0.16 mol of labile sulphur and 2.2 mol of iron per mol of protein. The enzyme is inhibited by NAD and cupferron competitively with ferricyanide, and by ATP (but not ADP) competitively with NADH. The enzyme is particularly thermostable, having a half-life at 95 degrees C of 35 min. The effect of temperature on the molar absorption coefficient and the stability of NADH was determined.
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PMID:A soluble NADH dehydrogenase (NADH: ferricyanide oxidoreductase) from Thermus aquaticus strain T351. 684 28


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