The effect of high pressure on peptide formation by the catalysis of carboxypeptidaseY (substitution of ester or peptide by amino acid derivative) or by thermolysin (condensation of N-acylamino acid and amino acid amide) was studied. The carboxypeptidase Y-catalyzed substitution reaction of N-[3-(2-furyl)acryloyl]phenylalanine ethyl ester with glycinamide or phenylalaninamide showed a six-fold higher
Dipeptide synthesis from N-[3-(2-furyl)acryloyl]-acylated (Fua-) amino acid ethyl ester and amino acid amide catalyzed by wheat bran carboxypeptidase (carboxypeptidase W) was studied. The optimum pH for peptide formation was at pH 8; more than 60% of the initial N-Fua-l-phenylalanine ethyl ester was converted to N-Fua-l-phenylalanylglycinamide under optimum conditions. The dependence of peptide formation on the concentration of amino acid amide showed an apparent saturation; this could be successfully explained by a reaction scheme which involved an acylated enzyme attacked by an enzyme-bound amine. The results for a reaction in the presence of two different amine components also supported this mechanism. Gly–NH2 had a better affinity to the acylated carboxypeptidase and the apparent dissociation constant (KN(app)) was about 50 mM. These results were compared with those for those reactions catalyzed by carboxypeptidases from yeast and malt.
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