Peptide Inhibitors and Activators of Carboxypeptidase B

A number of peptides containing d‐residues at the penultimate or C‐terminal position were tested for their ability to affect the carboxypeptidase‐B‐catalysed hydrolysis of basic and non‐basic peptides and esters. The effect of these modifiers, i.e. activation or inhibition is dependent on the nature of the modifier. The factors that determine the activity of the modifiers are: (a) the length of the peptide; (b) the basic or non‐basic nature of the C‐terminal and/or the penultimate residue and the optical configuration of these residues; (c) the substrate tested. The wide variations observed in the mode of activation and/or inhibition and the lack of correspondence between the K_i values is compatible with previous data on smaller inhibitors and larger peptide substrates, that the peptide and ester substrates of carboxypeptidase B occupy different loci on the enzyme.