Kinetic mechanism of ATP synthesis catalyzed by mitochondrial Fo x F1-ATPase.
Initial rates of succinate-dependent ATP synthesis catalyzed by submitochondrial particles from bovine heart substoichiometrically coupled with oligomycin were found to have hyperbolic dependencies on contents of Mg x ADP, free Mg2+, and phosphate. The results suggest that Mg x ADP complex and free phosphate are true substrates of the enzyme; and an unordered ternary complex of Fo x F1-ATPase, Mg x ADP, and phosphate is generated during the catalysis. The presence of free Mg2+ is required for the reaction. Mg2+ was a noncompetitive activator of ATP synthesis relative to Mg x ADP and a competitive activator relative to phosphate. The decrease in steady-state values of Deltamu(H)+ (by the inhibition of succinate oxidase with malonate) results in the decreased value of Vmax and in a slight decrease in Km for the substrates and Mg2+ without changes in affinity for the substrates. Based on these results, a kinetic scheme of ATP synthesis is proposed.
Galkin
M A
MA
Department of Biochemistry, School of Biology, Lomonosov Moscow State University, Moscow, 119899, Russia. adv@biochem.bio.msu.su
Syroeshkin
A V
AV
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D002384:Catalysis; D002417:Cattle; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D013367:Submitochondrial Particles / Q000201:enzymology; D013379:Substrate Specificity
D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases