Studies on Cytochrome c Peroxidase

Abstract

The peroxidatic oxidation of ferrocytochrome c catalyzed by yeast cytochrome c peroxidase was studied kinetically in the following combinations of substrates: H2O2-horse heart cytochrome c, C2H5OOH-horse heart cytochome c, H2O2-bakers' yeast cytochrome c, and C2H5OOH-bakers' yeast cytochrome c. Initial steady state rates of the overall reaction were analyzed according to the method of Dalziel in order to determine whether or not a ternary complex was involved in the reaction and in order to determine several rate constants of each step of the reaction. The cytochrome c peroxidase reaction appeared to follow the general form of a compulsory order mechanism for two substrate enzyme (Equations 1, 2, and 3). Kinetic evidence for the formation of a ternary complex of the enzyme, peroxide, and ferrocytochrome c was presented. A maximal turnover rate of the enzyme was determined to be extremely rapid; 2,600 sec-1 and 14,000 sec-1 at 23° for the substrate couples H2O2-horse heart ferrocytochrome c and H2O2-bakers' yeast ferrocytochrome c, respectively.