New chloride-activated aminopeptidase from human erythrocytes

Abstract

A new Cl −-activated aminopeptidase was purified from the cytosol of human erythrocytes as a single chain protein of an approx. M r, of 70 000 and p I of 5.1. The enzyme hydrolysed 2-naphthylamides of aliphatic, aromatic and basic L-amino acids, with a preference for the alanyl residue. It also hydrolysed di-, tri-, and some hydrophobic tetrapeptides. The inhibitors were bestatin, amastatin, Co 2+, Zn 2+, Mn 2+, 4-hydroxymercuribenzoate and 1,10-phenanthroline. The activity of the enzyme, inhibited by 4-hydroxymercuribenzoate, was partially restored by the addition of sulfhydryl compounds. The presence of 0.2 M Cl − (Br −, F −) caused a several-fold increase in the isolated aminopeptidase activity.