Cytochrome Oxidase Components 



337 



432 mji. Extraction of the haeniin from this preparation, and a study of the 

 chromatographic properties and spectra, showed that this preparation con- 

 tains both haemin a and cryptohaemin. The total haemin recovered was 

 lower, and the ratio of cryptohaemin to haemin a is greatly increased. 



These results suggest that cryptohaemin a is a product of oxidative degrada- 

 tion of haemin a. This degradation appears to be the result of an auto- 

 catalytic destruction of the prosthetic group of cytochrome a. It is interesting 



100 -I 



DAYS 



Fig. 1 . Loss of cytochrome c oxidase activity. The enzyme preparation was 

 allowed to stand at 4°C. 



to note that at high concentrations of chelate, the cytochrome oxidase 

 preparation is enzymically inactive and that degradation does not take place. 

 On dilution, the preparation is enzymically active and degradation does occur. 

 Since destruction of the enzyme is linked with enzymic activity and hence 

 with activation of oxygen, it is conceivable that this activated oxygen is the 

 cause of the destruction of the enzyme. Sekuzu, Takemori, Yonetani and 

 Okunuki (1959) have already presented spectrophotometric evidence that such 

 an activated form of the cytochrome does exist. 



The structure of the prosthetic group of the cytochromes has not been 

 neglected. The notable work of Marks, Dougall, Bullock and MacDonald 

 (1959) on the structure of the deuteroporphyrin derived from haemin a, 

 assigns the position and describes the nature of five of the groups substituted 

 on the eight available positions on the porphyrin nucleus. 



The problems which remain are: first to decide what are the three other 

 groups substituted on the porphyrin nucleus, and second, the arrangement of 

 these groups on the porphyrin nucleus. 



There is ample evidence to suggest the presence of a formyl group and a 



