N- and C-Terminal Residues in Baker's Yeast Cytochrome c

No acetyl peptide could be isolated from the enzymatic digests of baker's yeast cytochrome c unlike the mammalian heart cytochrome c. N-Succinyl-Thr.OH, N-succinyl.Thr.Glu.OH and N-succinyl-Thr.Glu.Phe.OH were isolated from the pronase, pepsin and chymotrypsin digests of the succinyl cytochrome c in which the terminal amino and ε-amino groups of lysine residues were succinylated. The N-terminal threonine was estimated in unexpectedly low yield by the DNP-method, whereas the PTC-rnethod demonstrated the N-terminal H.Thr.Glu—sequence in satisfactory yield. The C-terminal glutamic acid was established by the use of carboxypeptidase A on the succinylated cytochrome c. The N- and C-terminal residues in baker's yeast cytochrome c were thus established to be H.Thr.Glu.Phe—Glu.OH.