Application of carboxypeptidase C for peptide synthesis.

Carboxypeptidase C partially purified from the flavedo of citrus fruit by a new, simple procedure was studied as a catalyst for peptide-bond formation. Dipeptides were obtained in high yields (80-95%) with Bz--Tyr--OEt as carboxyl-compound, and amino acid amides and amino acid alkylesters as nucleophiles. To characterize the synthesis reaction, a number of parameters such as pH, excess of the nucleophile, and the molarity of the buffer were evaluated. The yield of dipeptides depends on the side chain of the amino acid alkylester used as the carboxyl component as well as on the N-terminal protecting group. Esterase activity was minimal in the absence of a nucleophile, suggesting a modified mechanism for the synthesis reaction compared to other serine proteases. No secondary hydrolysis of the peptides formed was observed.