MODE OF ACTION OF RESPIRATORY ENZYME 399 



mainly supported by the observation of Taniiya (JJ-li) that inliibition of the 

 respiration of yeast antl other organisms by cyanide has an effect on the 

 distribution coefficient of the oxidase, similar to that caused by a decrease 

 of substrate concentration ("unsaturation ' of the oxidase with substrate). 

 It would indeed by difficult to explain these observations on the basis of 

 Warburg's original theory of cyanide inliibition without postulating that 

 cyanide and carbon monoxide react with two different catalysts. It has 

 been shown, however, in Section 3. (5. '-2. that cyanide probably reacts with 

 both ferrous and ferric oxidase, and that the cyanide inhibition of respira- 

 tion requires a different interpretation. There is therefore no need for 

 assuming more than one enzyme. 



There is, moreover, no indication whatsoever of the occurrence of a 

 reaction : 



Fe'^^ O, + Fe^^ -> Fe';^ + Fe'^+ 



which is assumed in the dualistic theory, while the autoxidation of hemoglobin 

 appears to us a reasonably good model for the reaction: 



Fe'"^ 0.(H.,X) -f FeJ^ ^ FeJ^ (X) + Fe^+ + 2 OH" 

 assumed in our scheme above. 



