| Abstract: | The secretions (HPS) contained an arylamidase-like enzyme discovered by chromatography on Sephadex G-100 Superfine columns using N-L-alanyl-2-naphthylamine (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 L-alanine, L-leucine, L-methionine and L-phenylalanine, the pH optimum for the best substrate (ala-2NA) being 8.0, alpha-Benzoyl-DL-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- 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. |
