Elastases from human and canine granulocytes, I. Some proteolytic and esterolytic properties

Abstract

The lysosome-like granules of human and canine granulocytes contain an enzyme with elastinolytic activity. The enzymatic behaviour of these elastases was further characterized using the protein substrates elastin-orcein and azocasein and the synthetic substrates tert.-butyloxycarbonyl-alanine p-nitrophenylester (Boc-Ala-ONp) and 3-carboxypropionyl-L-alanyl-L-alanyl-L-alanine p-nitroanilide (Suc-Ala3-NHNp) in photometric assays. The affinities of the granulocyte elastases and of porcine pancreatic elastase to these substrates are very similar, e.g. human granulocyte elastase: KM (Boc-Ala-ONp) = 0.35mM, KM (Suc-Ala3-NHNp) = 1.25mM, porcine pancreatic elastase: KM (Boc-Ala-ONp) = 0.3mM, KM (Suc-Ala3-NHNp) - 1.15mM. The most convenient substrate for the assay of human and dog granulocyte elastases and for kinetic measurements with these enzymes is Suc-Ala3-NHNp. Using this substrate, the dissociation constant of the complex of human granulocyte elastase with human alpha1-antitrypsin could be determined (Ki = 3.5 x 10(-10)M).