Amino acid sequence around the active site aspartic acid in penicillopepsin

Penicillopepsin, the acid proteinase of Penicillium janthinellum, was specifically inactivated with diazoacetylnorleucine methyl ester. The peptide containing the glycollylnorleucine methyl ester group was isolated from a peptic digest. The amino acid sequence was found to be Ile∙Ala∙β(glycollyl-Nle OMe)-Asp∙Thr∙Gly∙Thr∙Thr∙Leu and is thus almost identical with the active site peptide of porcine pepsin: Ile∙Val∙Asp∙Thr∙Gly∙Thr∙Ser. This finding provides strong evidence for an evolutionary homology between penicillopepsin and porcine pepsin.