title: The concept of high- and low-affinity reactions in bovine cytochrome c oxidase steady-state kinetics.
abstract: (1) Analysis of the data from steady-state kinetic studies shows that two reactions between cytochrome c and cytochrome c oxidase sufficed to describe the concave Eadie-Hofstee plots (Km congruent to 1.10(-8) M and Km congruent to 2.10(-5) M). It is not necessary to postulate a third reaction of Km congruent to 10(-6) M. (2) Change of temperature, type of detergent and type of cytochrome c affected both reactions to the same extent. The presence of only single catalytic cytochrome c interaction site on the oxidase could explain the kinetic data. (3) Our experiments support the notion that, at least under our conditions (pH 7.8, low-ionic strength), the dissociation of ferricytochrome c from cytochrome c oxidase is the rate-limiting step in the steady-state kinetics. (4) A series of models, proposed to describe the observed steady-state kinetics, is discussed.
mesh_terms: D000818:Animals; D002417:Cattle; D019826:Cholic Acid; D002793:Cholic Acids / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006736:Horses; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology*; D009994:Osmolar Concentration; D013053:Spectrophotometry
chemical_list: D002793:Cholic Acids; D003574:Cytochrome c Group; D003576:Electron Transport Complex IV; D019826:Cholic Acid