Monkey Pepsinogens and Pepsins

IV. The Amino Acid Sequence of the Activation Peptide Segment of Japanese Monkey Pepsinogen

Abstract

The complete amino acid sequence of the activation peptide segment of the major component of Japanese monkey pepsinogens was determined. The pepsinogen was converted to pepsin by incubation at pH 2.0 and 14°C for 17min. The activation peptides were separated from the resulting pepsin and purified by chromatography on columns of sulfopropyl (SP)-Sephadex. One 25-residue peptide and two 22-residue peptides were isolated and their amino acid sequences were determined. The results showed that the former peptide was derived from the aminoterminal half (residues no. 1 to 25) and the latter peptides from the carboxyl-terminal half (residues no. 26 to 47) of the activation segment. The latter two peptides were identical except for a single amino acid replacement. The complete amino acid sequence of the whole activation peptide segment was thus deduced as follows:
¹Ile-Ile-Tyr-Lys-Val-Pro-Leu-Val-Arg-¹⁰Lys-Lys-Ser-Leu-Arg-Arg-Asn-Leu-Ser-Glu-²⁰His-Gly-Leu-Leu-Lys-Asp-Phe-Leu-Lys-Lys-³⁰His-Asn-Leu-Asn-Pro-Ala-Ser-Lys-Tyr-Phe-⁴⁰Pro-^Gln_Lys-Ala-Glu-Ala-Pro-Thr-⁴⁷Leu.
The whole chain was composed of 47 residues, and cleaved into two polypeptides by the cleavage of ²⁵Asp-²⁶Phe bond during activation. Two amino acids were detected at residue-41, i.e., glutamine and lysine, indicating the presence of two closely related pepsinogens in the sample used. The total number of residues (47) of the whole activation peptide segment is 3 and 2 residues larger than those of porcine pepsinogen and bovine pepsinogen, respectively. The differences are 15 and 22 residues as compared with porcine pepsinogen and bovine pepsignogen, respectively.