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Int J Med Sci 2008; 5(3):143-151. doi:10.7150/ijms.5.143

Research Paper

OXIDATIVE PHOSPHORYLATION: Kinetic and Thermodynamic Correlation between Electron Flow, Proton Translocation, Oxygen Consumption and ATP Synthesis under Close to In Vivo Concentrations of Oxygen

Baltazar D. Reynafarje1, Jorge Ferreira2

1. Johns Hopkins University School of Medicine, Department of Biological Chemistry, Baltimore, Maryland 21205, USA.
2. Programa de Farmacología Molecular y Clínica, Facultad de Medicina, Universidad de Chile, Independencia 1027, Casilla 70000 Santiago-7, Chile.

Abstract

For the fist time the mitochondrial process of oxidative phosphorylation has been studied by determining the extent and initial rates of electron flow, H+ translocation, O2 uptake and ATP synthesis under close to in vivo concentrations of oxygen. The following novel results were obtained. 1) The real rates of O2 uptake and ATP synthesis are orders of magnitude higher than those observed under state-3 metabolic conditions. 2) The phosphorylative process of ATP synthesis is neither kinetically nor thermodynamically related to the respiratory process of H+ ejection. 3) The ATP/O stoichiometry is not constant but varies depending on all, the redox potential (ΔEh), the degree of reduction of the membrane and the relative concentrations of O2, ADP, and protein. 4) The free energy of electron flow is not only used for the enzymatic binding and release of substrates and products but fundamentally for the actual synthesis of ATP from ADP and Pi. 5) The concentration of ADP that produces half-maximal responses of ATP synthesis (EC50) is not constant but varies depending on both ΔEh and O2 concentration. 6) The process of ATP synthesis exhibits strong positive catalytic cooperativity with a Hill coefficient, n, of ~3.0. It is concluded that the most important factor in determining the extent and rates of ATP synthesis is not the level of ADP or the proton gradient but the concentration of O2 and the state of reduction and/or protonation of the membrane.

Keywords: Energy transduction, proton gradient, free energy of electron flow and ATP synthesis

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How to cite this article:
Reynafarje BD, Ferreira J. OXIDATIVE PHOSPHORYLATION: Kinetic and Thermodynamic Correlation between Electron Flow, Proton Translocation, Oxygen Consumption and ATP Synthesis under Close to In Vivo Concentrations of Oxygen. Int J Med Sci 2008; 5(3):143-151. doi:10.7150/ijms.5.143. Available from http://www.medsci.org/v05p0143.htm