268 



LuciLE Smith and Helen Conrad 



greater than that of the whole homogenate when expressed in terms of the 

 content of cytochromes a plus a^. Addition of some of the soluble fraction of 

 the homogenate to the washed particles resulted in an inhibition of the 



Table 1. Inhibitory effect of salnqne on 



cytochrome c oxidase activity of heart 



muscle particles 



Heart muscle particles were prepared according to a modification of 



the Keilin-Hartree procedure. The concentration of cytochrome c 



in the test was 7 fiu. 



Table 2. Relationship of cytochrome c oxidase activity to content 

 OF cytochromes a + 03 in fractions of liver homogenate 



The oxidase assay and the method for measuring AE (difference in optical density between reduced 



and oxidized cytochromes a plus a^) are described in the section on Methods. The concentration of 



cytochrome c in the test was 15 ixu. 



Velocity constant 

 X dilution 



AE 605-630 m/t 



k|^E 



Whole liver homogenate 

 Supernatant from centri- 

 fuging homogenate at 

 900 rev/min for 5 min 

 Washed particles from 

 supernatant 



6-1 



6-8 

 7-6 



0-034 



0-024 

 0-008 



179 



281 

 950 



oxidase of the particles, but the inhibition was observed to be variable in 

 extent and to depend upon the concentration of cytochrome c. 

 Again the data indicate the necessity for caution in interpreting data on 



