Partial purification and characterization of arylamidases from human palatine secretions

Abstract

The secretions (HPS) contained an arylamidase-like enzyme discovered by chromatography on Sephadex G-100 Superfine columns using (2NA) as substrate. The enzyme was fractionated in the void volume, suggesting that its molecular weight was 150,000 or higher. It hydrolysed, with decreasing rates, the 2NA of -alanine, -leucine, -methionine and -phenylalanine, the pH optimum for the best substrate (ala-2NA) being 8.0. [alpha]-Benzoyl--arginine-2NA was not hydrolysed. p-Chloromercuribenzoate, EDTA, Ca2+ and Zn2+ were inhibitory, whereas chemical modification with typical tyrosyl group reagents did not significantly inactivate the enzyme. Treatment of HPS with Triton X-100 revealed two further arylamidase-like enzymes with lower mol. wt (90,000 and 40,000, respectively). Inhibition characteristics and Cl-1 effects suggest that one of these enzymes resembles aminopeptidase B (EC 3.4.11.6). HPS also contains endopeptidase activity over a wide pH range (6-9). The number of enzymes in HPS is thus small and most of the peptidolytic activity of HPS in vitro is due to one major enzyme with arylamidase activity.