[Amidation of proteins and peptides with carboxypeptidase Y]

The native and modified carboxypeptidase Y-catalyzed reaction of acyl transfer of acylamino acid and peptide residues from the corresponding esters to ammonia was studied. Use of the modified carboxypeptidase Y increased the yield of the resulting product. Calcitonin-Leu was transformed into human calcitonin.