296 



W. W. Wainio 



caused the loss of oxidized enzyme and the appearance of reduced enzyme, 

 viz., the 410 m// and 438 m/n peaks on the curve of the difference. 



We have also observed (Wainio, 1955d) that, whereas oxidized cytochrome 

 c oxidase is readily reduced by ferrocytochrome c in cyanide, the oxidation 



— *J00 



- 



-.100 



450 500 550 600 



Wave Lznqfh (mju) 



Fig. 4. Effect of cyanide on the spectrum of reduced cytochrome c oxidase. 



of reduced cytochrome c oxidase proceeds only very slowly in air in the 

 presence of cyanide. The slow rate is illustrated in Fig. 5 where the reciprocal 

 of the fraction of cytochrome c oxidase in the reduced state is plotted against 

 the time in minutes. The reaction is second order. These results would seem 

 to support the view that it is not the oxidized, but the reduced form of the 

 enzyme that is inhibited by cyanide. In order to reconcile this conclusion 

 with Warburg's observation that cyanide and oxygen do not compete for the 



