THE ACTIVATION AND INHIBITION OF TRYPSIN BY QUATERNARY AMMONIUM COMPOUNDS

Abstract

The effect of a variety of quaternary ammonium compounds upon the esterase activity of trypsin was investigated. Both activation and inhibition were observed; some compounds activated at low, but inhibited at higher, concentrations (group I), while others activated at high concentration (group II). Tetramethyl-, tetraethyl-, and tetra-n-propyl-ammonium bromides fell in group II, whereas tetra-n-butylammonium iodide fell in group I (50% inhibition at 0.52 mmolar). Dimethonium, pentamethonium, hexamethonium (2.25-fold activation at 0.08 M), heptamethonium, and decamethonium bromides belonged to group II. Activation by decamethonium bromide was greater at pH 7.2 than at pH 8.1 and was abolished by increasing the substrate concentration. Trypsin in the presence of 0.02 M calcium was activated only 11% by 0.03 M decamethonium bromide. An hypothesis offering a possible explanation of these observations is presented.