PROSTHETIC GROUPS, COENZYMES AND ENZYMES 



2 3 4 5 6 7 8 9 10 11 12 



Val-Glu(NH.)-Lys-Cy-Ala-Glu(NH..)-Cy-His-Thr-Val-Glu-Lys 



! i 



S hematin S 



Interestingly enough the hemopeptides from cytochromes c of 

 horse, beef, and pig had the same structure. In this part of the 

 molecule near the prosthetic group, therefore, the cytochromes 

 c from these different sources are identical, though species differ- 

 ences may of course occur in other parts of the molecule. 



Since Paleus, working in this institute, had produced pure 

 peptic degradation products of the cytochromes c from beef, 

 chicken, and salmon, Tuppy came to Stockholm for some time to 

 continue his research with Paleus (31). 



These peptic hemopeptides were considerably purer than 

 Tsou's. The iron content was 2.76%, and there were 20 

 nitrogen atoms per one Fe. The position of two additional 

 amino acids in the molecule was established, and the sequence of 

 aiTiino acids in the immediate vicinity of the prosthetic group in 

 the case of beef and salmon cytochromes c can now be con- 

 fidently asserted to be : 



12 3456 789 10 11 12 



— \'al-Glu(NH2)-Lys-Cy-Ala-Glu(NH2}-Cy-His-Thr-\-al-Glu-Lys 



The chicken cytochrome c showed a remarkable difference 

 from the other ones; it contained serine in the place of alanine 

 at position 5. The presence of a polar hydroxymethyl group 

 instead of the nonpolar methyl group of alanine so close to the 

 prosthetic group might be of functional importance, apart from 

 the interesting example that it provides of a species difference. 



Since two amino acids are interposed between the two heme- 



279 



