Enzymatic Peptide Synthesis. Carboxypeptidase Y Catalyzed Formation of Peptide Bonds

It is demonstrated that carboxypeptidase Y from Saccharomyces cerevisiae can catalyze the formation of peptide bonds using N-acylamino acid esters as substrates and free amino acids or amino acid amides as nucleophiles, The coupling yields observed with free amino acids were max. 60 % for alanine and lysine and they depended strongly on the reaction parameters; viz. pH, temperature and concentration of the amino acids as well as their structures. Importantly, under the conditions of peptide synthesis, the peptide product is not hydrolyzed. Amino acid amides were incorporated in higher yields (60-95%) which were less sensitive to the experimental conditions and the structures of this type of nucleophile. The present study suggests that carboxypeptidase Y, having a broad specificity for amino acid side chains, may become a general catalyst for enzymatic peptide synthesis in the homogeneous phase.