BRITTON CHANCE 



43 



Application of This Equation to the Kinetics of Cytochrome a.^ and 

 Oxygen. Equation 5 above has a sound theoretical basis for the peroxi- 

 dase-type kinetics, and it is very probable that it is an approximation to 



Fig. 4. Effect of temperature 

 on the reaction velocity con- 

 stants ki and k4 as determined 

 according to equations 5 and 6 

 (from experimental data similar 

 to that in fig. 3). The heats of 

 activation are indicated for the 

 two velocity constants. (The 

 limitations to the interpretation 

 of these data are described in 

 the text, expt. 630a.) For more 

 details see ref. 16. Data from 

 Arch. Biochem. 



75 



.3C 



o 



O 



^ 7.0 • 



6.0- 



5.5 



o 

 o 



5.0 



10,000 



-I r I t T I I T ■■ "T 



3.0 3.5 



^3 



4.0 



_I0_~ 



T 



K 



8.0 



o 



9.300 calories 



3.0 3.5 4.0 



10^ o^ 



Fig. 5. A plot of the values of 

 ki computed for the reaction of 

 oxygen with cytochrome as of 

 baker's yeast cells according to 

 equation 5. The large value of 

 heat of activation suggests the 

 presence of intermediate com- 

 pounds between oxygen and 

 cytochrome as (expt. 630b). For 

 more details see ref. 16. 



the value of ki for the more complex cytochrome type kinetics, especially 

 when the cycle of oxidation and reduction of the cytochrome has a reason- 

 able 'plateau.' Experimentally, it is easy to apply this equation to cyto- 

 chrome kinetics, and some very preliminary results are included in figure 

 5. The value of ki which has been determined in these conditions agrees 

 rather well with preliminary values for ki obtained in the rapid flow 



