Properties and kinetics of salt activation of a membrane-bound NADH dehydrogenase from a marine bacterium Photobacterium phosphoreum.
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.
D000838:Anions / Q000494:pharmacology; D002414:Cations, Monovalent / Q000494:pharmacology; D002856:Chromatophores; D004789:Enzyme Activation; D007700:Kinetics; D008566:Membranes / Q000201:enzymology; D008722:Methods; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D009994:Osmolar Concentration; D010776:Photobacterium / Q000166:cytology / Q000201:enzymology*; D013379:Substrate Specificity
D000838:Anions; D002414:Cations, Monovalent; D009247:NADH, NADPH Oxidoreductases