The primary structure of carboxypeptidase S1 from Penicillium janthinellum

Abstract
The complete amino acid sequence of carboxypeptidase Sl from Penicillium janthinellum has been determined by N‐terminal sequencing of the reduced and vinylpyridinated protein and of peptides obtained by cleavage with cyanogen bromide, iodosobenzoic acid, hydroxylamine, endoproteinase LysC, endoproteinase AspN and Glu‐specific proteinase from B. licheniformis. The enzyme consists of a single peptide chain of 433 amino acid residues and contains 9 half‐cystine residues and one glycosylated asparagine residue. A comparison to other carboxypeptidases shows that the enzyme is homologous to carboxypeptidase‐Y and carboxypeptidase‐MIII from malt. Specificity and binding of substrates are discussed from a three‐dimensional model based on the known structure of carboxypeptidase‐Y from Saccharomyces cereviciae and carboxypeptidase II from wheat.