Carboxypeptidase Y catalyzed transpeptidations and enzymatic peptide synthesis

Abstract

It is shown that carboxypeptidase Y, in addition to its known amidase and peptidase activities, also exhibits peptidyl-amino-acid-amide hydrolase activity, i.e., amino acid amides are released from peptide amides. These three activities were investigated as to their usefulness in catalyzing transpeptidation reactions in the presence of suitable nucleophiles. Using peptides and peptide amides as substrates and amino acids or amino acid amides as nucleophiles, it could be shown that transpeptidation products were formed in accordance to each of the above mentioned activities of carboxypeptidase Y. While transpeptidation via the amidase activity results in an elongation of the peptide chain, transpeptidation via peptidase activity results in the exchange of the C-terminal amino acid residue. If the substrate is a peptide amide, transpeptidation via the peptidyl-amino-acid-amide hydrolase activity will result in the formation of a peptide where the C-terminal amino acid amide is replaced by either an amino acid or an amino acid amide.