Pfizer Handbook o£ Microbial Metabolites 



448 



to porphyrin nitrogen, the other two to histidyl residues 

 in the protein. 



Proteolytic enzyme degradation of cytochrome c has 

 yielded the polypeptide fragment in the vicinity of the 

 porphyrin, and the amino acid sequence has been de- 

 termined. It is thought to be:'"'* 



histidyl vaiyl-glutamyl-lysyl-cysteinyl 



alanyl 



glutamyl 



iysyl-glutamyl-vaiyl-threonyi-histidyi-cysteinyl 



Cytochrome c Fragment (Hemopeptide) 



Bovine cytochrome c has a particle weight of about 

 13,000 and contains about 20 lysine and 3 or 4 histidine 

 residues. A helical model of the Pauling type thus prob- 

 ably showns the entire active region of the enzyme since 

 this cytochrome contains only one prosthetic group. 



Cytochromes (c^ and Cr,) isolated from Azotobacter 

 vinelandii have a particle weight of about 12,000 and con- 

 tain 0.46% iron, so that superficially they resemble mam- 

 malian cytochrome c.^^ In a comparative study of mam- 

 mahan and bacterial (Pseudomonas aerugmosa) cyto- 



s«Hans Tuppy and G. Bodo, Monatshefte Chem. 85 1024, 1182 

 (1954); Hans Tuppy and Sven Paleus, Acta Chem. Scand. 9 353, 365 

 (1955). 



59 A. Tissieres, Biochem. J. 64 582 (1956). 



