Studies on the mechanism of oxidative phosphorylation. Flow-force relationships in mitochondrial energy-linked reactions.
The relationship between the steady-state level of membrane potential (delta psi) and the rates of energy production and consumption has been studied in mitochondria and submitochondrial particles. The energy-linked reactions investigated were oxidative phosphorylation (with NADH, succinate, and beta-hydroxybutyrate as respiratory substrates) and nucleoside triphosphate-driven transhydrogenation from NADH to NADP and uphill electron transfer from succinate to NAD. Results have shown the following. 1) Attenuation of the rates of the energy-producing reactions results in a parallel change in the rates of the energy-consuming reactions with little or no change in the magnitude of steady-state delta psi. 2) At low rates of energy production and consumption, steady-state delta psi decreases. However, this is due largely to the energy leak of the system which lowers static-head delta psi when the rate of energy production is slow. 3) When the rate of energy production and static-head delta psi are held constant, and the rate of energy consumption is diminished by partial inhibition or the use of suboptimal conditions (e.g. subsaturating substrate concentrations), then even a small decrease in the rate of energy consumption results in an upward adjustment of the level of steady-state delta psi. The lower the rate of energy input, the greater the upward adjustment of steady-state delta psi upon suppression of the rate of energy consumption. 4) The above results have been discussed with regard to the role of bulk-phase delta mu H+ or delta psi in the mitochondrial energy transfer reactions.
Matsuno-Yagi
A
A
Department of Basic and Clinical Research, Scripps Clinic and Research Foundation, La Jolla, California 92037.
Hatefi
Y
Y
D000818:Animals; D002417:Cattle; D004579:Electron Transport; D004734:Energy Metabolism; D007700:Kinetics; D008930:Mitochondria, Liver / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010085:Oxidative Phosphorylation; D051381:Rats; D013367:Submitochondrial Particles / Q000378:metabolism*
D009243:NAD; D009249:NADP