FURTHER OBSERVATIONS ON HISTOCHEMICAL ESTERASE AND AMIDASE ACTIVITIES WITH SIMILARITIES TO TRYPSIN

Abstract

When the histochemical substrates benzoyl-dl-arginine β-naphthylamide, benzoyl-dl-lysine β-naphthylamide, Naphthol AS and AS-D ε-aminocaproate, and Naphthol AS β-alanyl glycinate were tested with tissue sections and as substrates for purified enzymes, a species-limited enzyme activity having substrate specificity and enzymic kinetic and affector characteristics strikingly similar to those of bovine trypsin was noted in human mast cells. The ester substrates were hydrolyzed in several other tissue sites, and, in those tested, hydrolysis appeared to be related to the activity of an aliesterase(s) with substrate specificity and affector characteristics markedly different from those of bovine trypsin. Although Naphthol AS chloroacetate has been defined as a substrate for a chymotrypsin-like enzyme in rat mast cells, the definite possibility exists that its hydrolysis in human mast cells in fresh frozen tissue sections may be due at least its part to the activity of a trypsin-like enzyme.