[The effect of anionic complexes on cytochrome c oxidation by cytochrome c oxidase]

The effect of different buffer anions on the maximal velocity (Vmax) and Michaelis constant (Km) of the first reaction between horse cytochrome c and beef cytochrome c oxidase was studied. The Michaelis constant for the high affinity phase varies little as the buffer anions borate, phosphate, succinate and citrate were employed, but Vmax varies significantly. At the ionic strength I = 0.1 and pH 7.4 the Vmax increases in the order as following: borate < phosphate < succinate < > citrate. citrate. The differences in maximal activities in the presence of the anions may result from the changes in anion binding side on cytochrome c that affect its interaction with cytochrome c oxidase. The effect of the phosphate, succinate and citrate anions on the electron transfer reaction between cytochrome c and cytochrome c oxidase is important as a control of the respiration process in mitochondria at physiological conditions.