Hydrolysis Catalyzed by Exopeptidases

Aminopeptidases catalyze the hydrolysis of the peptide bond which follows the N-terminal residue (A). As a consequence, the second residue (B) becomes N-terminal and is cleaved off 

The limitations noted for aminopeptidases are true for carboxypeptidases as well. The pancreatic enzyme carboxypeptidase A shows low rates in the hydrolysis of peptides with a basic amino acid (arginine or lysine) as the C-terminal residue. Carboxypeptidase B is particularly effective when the same basic residues occupy the C-terminal position. The yeast enzyme carboxypeptidase Y is less specific and therefore more generally applicable, but probably still unsuited for the elucidation of a longer sequence. 

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