Biomaterial Database

Properties of respiratory chain-linked Na(+)-independent NADH-quinone reductase in a marine Vibrio alginolyticus. 1992

M Hayashi, and T Miyoshi, and M Sato, and T Unemoto

Laboratory of Membrane Biochemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.

The respiratory chain of a marine Vibrio alginolyticus contains two types of NADH-quinone reductase (NQR): one is an Na(+)-dependent NQR functioning as an Na+ pump (NQR-1) and the other is an Na(+)-independent NQR (NQR-2). NQR-2 was purified about 55-fold from the membrane of mutant Nap-1 which is devoid of NQR-1, and its properties were compared with those of NQR-1. In contrast to NQR-1, the purified NQR-2 does not require any salts for activity and is not inhibited by up to 0.4 M salts. The optimum pH of NQR-2 is between 6.8 and 7.8, which is about 0.7 ph units lower than that of NQR-1. NQR-2 is insensitive to strong inhibitors of NQR-1 such as p-chloromercuribenzoate, Ag+ and 2-heptyl-4-hydroxyquinoline N-oxide. Using inverted membrane vesicles, it was confirmed that NQR-2 has no capacity to generate a membrane potential. NQR-2 reduces menadione and ubiquinone-1 by a two-electron reduction pathway. Since the NADH-reacting FAD-containing beta-subunit of NQR-1 reduces quinones by a one-electron reduction pathway, the mode of quinone reduction is closely related to energy coupling; the formation of semiquinone radicals as an intermediate is likely to be essential to functioning as an ion pump.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009097	Multienzyme Complexes	Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates. They may involve simply a transfer of water molecules or hydrogen atoms and may be associated with large supramolecular structures such as MITOCHONDRIA or RIBOSOMES.	Complexes, Multienzyme
D010088	Oxidoreductases	The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)	Dehydrogenases,Oxidases,Oxidoreductase,Reductases,Dehydrogenase,Oxidase,Reductase
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D013385	Succinate Dehydrogenase	A flavoprotein containing oxidoreductase that catalyzes the dehydrogenation of SUCCINATE to fumarate. In most eukaryotic organisms this enzyme is a component of mitochondrial electron transport complex II.	Succinic Oxidase,Fumarate Reductase,Succinic Dehydrogenase,Dehydrogenase, Succinate,Dehydrogenase, Succinic,Oxidase, Succinic,Reductase, Fumarate
D014733	Vibrio	A genus of VIBRIONACEAE, made up of short, slightly curved, motile, gram-negative rods. Various species produce cholera and other gastrointestinal disorders as well as abortion in sheep and cattle.	Beneckea
D016660	NAD(P)H Dehydrogenase (Quinone)	A flavoprotein that reversibly catalyzes the oxidation of NADH or NADPH by various quinones and oxidation-reduction dyes. The enzyme is inhibited by dicoumarol, capsaicin, and caffeine.	DT Diaphorase,Menadione Reductase,Phylloquinone Reductase,Quinone Reductase,Vitamin K Reductase,Diaphorase, DT,Reductase, Menadione,Reductase, Phylloquinone,Reductase, Quinone,Reductase, Vitamin K
D042963	Electron Transport Complex II	A flavoprotein oxidase complex that contains iron-sulfur centers. It catalyzes the oxidation of SUCCINATE to fumarate and couples the reaction to the reduction of UBIQUINONE to ubiquinol.	Succinate Dehydrogenase (Ubiquinone),Succinate Dehydrogenase-CoQ Reductase,Succinate Dehydrogenase-Coenzyme Q Reductase,Succinate-Coenzyme Q Reductase,Succinate-Q Oxidoreductase,Succinate-Quinone Oxidoreductase,Succinate-Ubiquinone Oxidoreductase,Succinate-Ubiquinone Reductase,Dehydrogenase-CoQ Reductase, Succinate,Oxidoreductase, Succinate-Q,Oxidoreductase, Succinate-Quinone,Oxidoreductase, Succinate-Ubiquinone,Reductase, Succinate Dehydrogenase-CoQ,Succinate Coenzyme Q Reductase,Succinate Dehydrogenase CoQ Reductase,Succinate Dehydrogenase Coenzyme Q Reductase,Succinate Q Oxidoreductase,Succinate Quinone Oxidoreductase,Succinate Ubiquinone Oxidoreductase,Succinate Ubiquinone Reductase