Inhibition of aminoacylase from hog kidney by 2-ethoxy-1-(ethoxycarbonyl)-1,2-dihydroquinoline.

Aminoacylase is inactivated by 2-ethoxy-1-(ethoxycarbonyl)-1,2-dihydroquinoline (EEDQ), a specific carboxyl reagent; inactivation is pH-dependent. The inhibition kinetics were of the first-order type. pH titration shows that half-maximal inactivation is obtained at pH 6.0 +/- 0.2, suggesting that the EEDQ reactive carboxyl group has a rather high pK value. Protection against EEDQ inactivation of the enzyme is afforded by competitive inhibitors, most effectively by tosyl-L-phenylalanine. These results suggest that a carboxyl group is located at or near the active site of the enzyme. A possible function of the carboxyl group in the catalytic process is proposed.