COMPARATIVE STUDIES ON HUMAN CARBOXYPEPTIDASE-B AND CARBOXYPEPTIDASE-N

A series of dicarboxylic acid bi-product analogs of lysine and arginine have been tested as competitive inhibitors of human pancreatic carboxypeptidase B and human plasma carboxypeptidase N. The most effective derivative was guanidinoethylmercaptosuccinic acid with Kis of 0.5 and 1.0 × 10-6 m for Carboxypeptidases B and N, respectively. Values for the all-carbon guanidinopropylsuccinic acid were similar. In addition the kinetic parameters, Km and kcat Km, have been determined for the hydrolysis of benzoyl-alanyl-lysine and benzoylalanyl-arginine by human Carboxypeptidases B and N. These substrates have been proposed for use in improved spectrophotometric assays. An enhanced affinity of these substrates versus benzoyl-glycyl-lysine or benzoyl-glycyl-arginine indicates a significant participation of the penultimate amino acid in catalysis of substrate. © 1979.