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 membrane-bound NADH dehydrogenase, solubilized and partially purified from a marine bacterium Photobacterium phosphoreum, contains FAD as the prosthetic group, and is specific for NADH. Ferricyanide, various other redox dyes and cytochrome c can act as electron acceptors. The enzymatic activity when assayed with electron acceptors other than cytochrome c, is activated by monovalent cations (Na+ and K+) and deactivated by high concentrations of monovalent anions (SCN-, NO3-, and Cl-) but not by phosphate ions. The enzymatic reaction follows a ping-pong mechanism and kinetic analysis of the enzyme showed that the activation by monovalent cations is due to increase of affinity of the enzyme for substrates; Vm was not affected. The increase of affinity was 62- and 46-fold for NADH and 57- and 31-fold for 2,6-dichlorophenol indophenol in the presence of Na+ and K+, respectively. On the other hand, NADH-cytochrome c reductase activity of the enzyme was strongly inhibited by these cations.
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PMID:Properties and kinetics of salt activation of a membrane-bound NADH dehydrogenase from a marine bacterium Photobacterium phosphoreum. 72 93

Coenzyme Q is required in the electron transport system of rat hepatocyte and human erythrocyte plasma membranes. Extraction of coenzyme Q from the membrane decreases NADH dehydrogenase and NADH:oxygen oxidoreductase activity. Addition of coenzyme Q to the extracted membrane restores the activity. Partial restoration of activity is also found with alpha-tocopherylquinone, but not with vitamin K1. Analogs of coenzyme Q inhibit NADH dehydrogenase and oxidase activity and the inhibition is reversed by added coenzyme Q. Ferricyanide reduction by transmembrane electron transport from HeLa cells is inhibited by coenzyme Q analogs and restored with added coenzyme Q10. Reduction of external ferricyanide and diferric transferrin by HeLa cells is accompanied by proton release from the cells. Inhibition of the reduction by coenzyme Q analogs also inhibits the proton release, and coenzyme Q10 restores the proton release activity. Trans-plasma membrane electron transport stimulates growth of serum-deficient cells, and added coenzyme Q10 increases growth of HeLa (human adenocarcinoma) and BALB/3T3 (mouse fibroblast) cells. The evidence is consistent with a function for coenzyme Q in a trans-plasma membrane electron transport system which influences cell growth.
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PMID:Requirement for coenzyme Q in plasma membrane electron transport. 145 89

The reductant dependence of iron mobilization from isolated rabbit reticulocyte endosomes containing diferric transferrin is reported. The kinetic effects of acidification by a H(+)-ATPase are eliminated by incubating the endosomes at pH 6.0 in the presence of 15 microM FCCP to acidify the intravesicular milieu and to dissociate 59Fe(III) from transferrin. In the absence of reductants, iron is not released from the vesicles, and iron leakage is negligible. The second-order dependence of rate constants and amounts of 59Fe mobilized from endosomes using ascorbate, ferrocyanide, or NADH are consistent with reversible mechanisms. The estimated apparent first-order rate constant for mobilization by ascorbate is (2.7 +/- 0.4) x 10(-3) s-1 in contrast to (3.2 +/- 0.1) x 10(-4) s-1 for NADH and (3.5 +/- 0.6) x 10(-4) s-1 for ferrocyanide. These results support models where multiple reactions are involved in complex processes leading to iron transfer and membrane translocation. A type II NADH dehydrogenase (diaphorase) is present on the endosome outer membrane. The kinetics of extravesicular ferricyanide reduction indicate a bimolecular-bimolecular steady-state mechanism with substrate inhibition. Ferricyanide inhibition of 59Fe mobilization is not detected. Significant differences between mobilization and ferricyanide reduction kinetics indicate that the diaphorase is not involved in 59Fe(III) reduction. Sequential additions of NADH followed by ascorbate or vice versa indicate a minimum of two sites of 59Fe(III) residence; one site available to reducing equivalents from ascorbate and a different site available to NADH. Sequential additions using ferrocyanide and the other reductants suggest interactions among sites available for reduction. Inhibition of ascorbate-mediated mobilization by DCCD and enhancement of ferrocyanide and NADH-mediated mobilization suggest a role for a moiety with characteristics of a proton pore similar to that of the H(+)-ATPase. These data provide significant constraints on models of iron reduction, translocation, and mobilization by endocytic vesicles.
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PMID:Kinetic characterization of reductant dependent processes of iron mobilization from endocytic vesicles. 153 18

The steady-state kinetics of oxidation of the mitochondrial NADH: ubiquinone oxidoreductase (complex I, EC 1.6.99.3) by artificial electron acceptors--p-quinones and inorganic complexes has been investigated. A limiting stage in the NADH: ferricyanide reductase reaction is a reductive half-reaction. Ferricyanide interacts with negative-charged protein groups taking part in the NADH binding. The rate constants of the quinone reduction by complex I vary from 1.10(6) to 4.10(3) M-1s-1. The NADH, NAD+ and ADP-ribose inhibition data indicate that oxidizers in the rotenono-insensitive reaction interact with the redox centre near the NAD+/NADH binding site, most probably with FMN.
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PMID:[Reaction of complex I of the mitochondrial electron transport chain with artificial oxidizers]. 251 53

Ferricyanide is actively reduced by intact maize (Zea mays L., var XL 342) roots. This reduction is salt and temperature dependent, is stimulated by fusicoccin, and is accompanied by decrease of external pH. In anaerobic conditions, ferricyanide partially restores fusicoccin-induced proton extrusion. A salt-, temperature-, and pH-dependent cyanide-insensitive NADH-ferricyanide oxidoreductase activity can be demonstrated in microsomes isolated from the same plant tissue. This evidence supports the hypothesis, as proposed by Craig and Crane (1982 Plant Physiol 67: S-558, S-835), that the ferricyanide reduction is carried out by a transmembrane NADH dehydrogenase.
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PMID:A transplasmamembrane electron transport system in maize roots. 1666 72