Action of Serine Carboxypeptidases on Endopeptidase Substrates, <i>N</i>-Acyldipeptideamides

Abstract

Abstract Action patterns of two serine carboxypeptidases, one from yeast (Y) and the other from wheat bran (W), on N-[3-(2-furyl)acryloyl]-(Fua-) dipeptideamide substrates were examined by HPLC and amino acid analysis. In the reaction of the wheat enzyme the substrates were hydrolyzed to Fua-amino acid and no sufficient amount of Fua-dipeptides were detected on HPLC in the product mixtures. Very few or no free amino acids were observed by amino acid analysis. This indicates that the wheat enzyme exhibited carboxamidopeptidase activity on these substrates. On the contrary, carboxypeptidase Y gave Fua-amino acids and Fua-dipeptides as products, depending on the structure of the substrates. Accordingly, liberations of free amino acids were detected in some cases. This result shows that the yeast enzyme acts on some of the substrates in a two step manner: First by amidase and second by a carboxypeptidase activity. Based on these results the substrate binding mechanisms of these enzymes are discussed.