title: The effect of energization on the apparent Michaelis-Mentne constant for oxygen in mitochondrial respiration.
abstract: Lineweaver-Burk plots of 1/v against 1/[O(2)] for rat liver mitochondrial respiration with succinate or ascorbate+NNN'N'-tetramethyl-p-phenylenediamine as substrates are non-linear. In state 3u (uncoupled by trifluoromethoxycarbonyl cyanide phenylhydrazone) such plots tend to be concave upward, whereas in state 4 (energized) the plots were concave downward. The apparent K(m) for oxygen is larger in state 4 than in state 3u, despite the higher turnover in the latter system. It is postulated that at least one reversible reaction occurs between cytochrome c and cytochrome c oxidase, whose rate is increased on energization (reversed electron transfer); a model including such a reaction is proposed which accounts semiquantitatively for the observations.
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism; D003201:Computers; D003574:Cytochrome c Group / Q000378:metabolism; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism; D007700:Kinetics; D008433:Mathematics; D008930:Mitochondria, Liver / Q000378:metabolism*; D008954:Models, Biological; D010101:Oxygen Consumption; D010655:Phenylenediamines / Q000378:metabolism; D051381:Rats; D013386:Succinates / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; D010655:Phenylenediamines; D013386:Succinates; D003576:Electron Transport Complex IV; D001205:Ascorbic Acid