Inhibition of aminopeptidase N by two synthetic tripeptides

Abstract

MR-387A1 (AHPA-Val-Pro) and A2 (AHPA-Val-Hyp) were prepared as aminopeptidase N inhibitors through the synthesis of peptide MR-387A and B analogues which contained 3-amino-2-hydroxy-4-phenyl butanoic acid (AHPA) as a zinc-chelating moiety. They are competitive inhibitors of aminopeptidase N with inhibition constants(Ki) of 4.1×10-7 and 1.1×10-6 M, respectively. MR-387A1 also strongly inhibited aminopeptidase B of human myelogenous leukemia K-562 cell with IC50 of 0.35 μM. Inhibitions of aminopeptidase N activity by AHPA-bearing inhibitors of various peptide chain lengths also have been studied. IC50 values of AHPA-Val (bestatin), AHPA-Val-Pro (MR-387A1) and AHPA-Val-Pro-Leu (MR-387C) compared against porcine kidney aminopeptidase N were 20.1, 0.60 and 0.08 μM, respectively. These results support that a multiple interaction between the S1→S′3 sites of aminopeptidase N and the P1→P′3 of the inhibitor plays a crucial role in stabilizing strongly the enzyme-inhibitor complex.