On the Active Sites of Proteases

The degree of Stereospecificity exhibited by carboxypeptidase A is dependent on the structural features of the substrate employed. Carboxypeptidase A can effectively split the C‐terminal d ‐alanine residue from peptides that are strongly bound to the enzyme through interactions distant from the catalytic center (in subsites S 2 and S 3 ). From studies using strongly interacting substrates it may be concluded that carboxypeptidase A shows a higher degree of stereospecificity toward the penultimate amino acid residue than toward the C‐terminal residue.