An Inhibitor of Trypsin-Like Activity in Rat Liver

Inhibitors of lysosomal and tryptic hydrolysis of benzoyl-dl-arginine-β-naphthylamide (BANA) were shown to be present in the microsomal and 100,000g supernatant fractions of rat liver homogenates. The 100,000g soluble inhibitor was shown to be: (1) capable of inhibiting tryptic digestion of casein and BANA; (2) insoluble at pH 4.0 but soluble at neutral or basic pH values; (3) nondialyzable; and (4) heat-stable. The inhibitor was maximally active at pH 7.4 and above during lysosomal hydrolysis of BANA.