[Mitochondrial menadione reductase: kinetics and mechanism of the action in situ].
The formal mechanism of action of menadion reductase localized in the membrane of intact mitochondria in the rebox reaction of 4-N (p-sulfoanilin)-5-methoxy-1,2-benzoquinone with NADH as an electron donor has been studied by the stationary kinetics method. It has been shown that the mitochondrial menadion reductase incorporated into the membrane functions according to the "ping-pong" mechanism, similar to the functioning of the free enzyme. However, in this case an inhibitory effect of NADH has been noticed. A phenomenological equation, which is in a good accordance with the experimental data, has been suggested. Luminescence studies showed that a specific NADH-binding site located outside the active centre exists in the enzyme molecule. The model of the mechanism of the enzyme substrate inhibition in situ, responsible for a change in the conformation of the apoenzyme occurs upon NADH binding, is discussed.
D000818:Animals; D001051:Apoenzymes / Q000378:metabolism; D001665:Binding Sites; D007700:Kinetics; D008566:Membranes / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D011487:Protein Conformation; D011808:Quinone Reductases / Q000378:metabolism*; D051381:Rats
D001051:Apoenzymes; D009243:NAD; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases
Mitokhondrial'naia menadionreduktaza kinetika i mekhanizm deĭstviia fermenta in situ