Carboxypeptidase inhibitors from Ascaris suum: the primary structure.

The carboxypeptidase A inhibitor from Ascaris suum was isolated from aqueous extracts by affinity chromatography toward immobilized carboxypeptidase A. The amino acid sequence is DQVRKCLSDT10DCTNGEKCVQ20KNKICSTIVE30IQRCEKEHFT40IPCKSNNDCQ50VWAHEKICN K60LPWGL65 . The carboxypeptidase A inhibitor is not homologous with the chymotrypsin/elastase or trypsin inhibitors from Ascaris, but shows homology in a 9-residue internal sequence with the 37/39-residue carboxypeptidase inhibitors from tomato and potato. The carboxy-terminal 5 (4) residues in the three inhibitors are similar, suggesting a common mechanism of inhibition.