Studies on Problems of Cytochrome c Oxidase Assay 



265 



Figs. 2a and 2b. The different curves were obtained in experiments with two 

 different purified preparations and two preparations of heart muscle particles. 

 Measurements made with mixtures of ferro- and ferricytochrome c showed 

 that the velocity constant is dependent upon the total concentration of 

 cytochrome c (ferro- plus ferri-) in the reaction mixture. This is illustrated by 



5-.l^ 20 30 40 50 60 7D 80 90 100 110 120 

 Cytochrome c cone., //M 



20 30 40 50 60 70 80 

 Cytochrome c cone., //M 



B 



Fig. 3. Variation of the initial rate of oxidation of cytochrome c with the total 

 concentration of cytochrome c in the test mixture. The initial rates were calcu- 

 lated from the data of Fig. 2 by multiplying the rate constants by the concentration 

 of ferrocytochrome c in the test mixture. 



