Carboxypeptidase mediated C-terminal amidation of polypeptide acids.

The possibilities of obtaining polypeptide amides in good yields from polypeptide acids by carboxypeptidase catalyzed transpeptidation have been investigated in different C-terminal amidations catalysed by CPD-Y, placing particular emphasis on the structure of the leaving group. In models for GRF(1-29) acid, larger hydrophilic leaving groups like threonine were particularly useful in reactions with arginine amide acting as nucleophile. In models for calcitonin acids, good results were obtained using also large hydrophobics like methionine and tryptophane in amidations with ammonia acting as nucleophile. Influences on both rate and synthetic efficiency of similar trend, but different magnitude, were observed in both salmon and human calcitonin models and high yields were attainable also in longer peptides or if recombinant secreted enzyme was employed.