Primary structure of peptides which form the disulfide bonds of chicken pepsin

Abstract

The molecule of chicken pepsin is cross-linked by three disulfide bonds. The structures of the half-cystine peptides which form these bonds were determined by the analysis of different enzymic digests of the enzyme. The order of the disulfide bonds in the molecule was elucidated with regard to sequential homologies between chicken pepsin and other acid proteases. The three disulfide bonds of chicken pepsin, numbered from the N-terminus of pepsin, are: 1st bond Ile-Tyr-Cys-(Lys-Ser-Ser-Ala)-Cys-Ser-Asn-His-Lys; 2nd bond Val-Ala-Cys-Cys-(Thr-Phe)-Gln-Ala; 3rd bond Asp-Leu-Gly-Val-Ser-Ser-Asp-Gly-Glu-Ile-Ser-Cys-(Asp-Asp-Ile-Ser-Lys-Leu-Pro-Asp)-Cys-(Ser-Gly-Asp-Glu-Asn-Leu-Val)-Met.