Effect of diethylpyrocarbonate on human gastric mucosa acid proteinases: zymogen activation

Proteolytic activity (with hemoglobin as the substrate, and at a pH of 3.8) of human gastric mucosa homogenates can be separated into two peaks by DEAE-cellulose column chromatography. One of the peaks contains a proteolytic enzyme that is activated some 11-fold by exposure to pH 3.5, and is also activated by preincubation with diethylpyrocarbonate. The other peak contains a proteolytic enzyme that is not activated at low pH values, and is inactivated by preincubation with diethylpyrocarbonate. The enzyme activity arising out of acid activation is partially lost by exposure to pH 8.5 (pepsin-like enzyme). The nonactivated enzyme is resistant to alkaline pH (cathepsin-like enzyme).