Inhibition of Tryptic Activity by Various Synthetic Inhibitors

Abstract

The inhibitory effects of various derivatives of L-lysine and [epsilon]-amino-caproic acid on the caseinolytic, amidase and esterase activities of trypsin were examined. Weak inhibitory effects on the amidase and esterase activities were observed with n-butylamine, L-lysine, N-benzoyl-L-lysine and [epsilon] -aminocaproic acid, more on the amidase activity than on the esterase activity. Various esters of N-benzoyl-L-lysine and methyl N-tosyl-L-arginate inhibited the caseinolytic activity strongly, but these compounds were typical substrates of trypsin. Therefore, these esters seem to cause inhibition by being hydrolyzed in place of casein. Little inhibition of amidase and esterase activities was observed with butyl N-carbobenzoxy-L-lysinate. Extensive inhibition of caseinolytic activity was observed with various esters of [epsilon]-amino caproic acid, and the order of their effects was hexyl > heptyl > amyl >butyl >isoamyl >isobutyl >isopropyl < methyl. From the methyl to the hexyl ester, the longer the carbon chain of the ester moiety, the greater was the inhibitory effect; the effects of branched carbon chain esters were less than those of the corresponding straight chain esters. The esterolytic activity of trypsin on these esters was very small; the rate decreased with increased length of the carbon chain of the ester moiety. Thus, the potent inhibitory effect of hexyl [epsilon] -aminocaproate strongly inhibited the hydrolysis of various synthetic substrate esters by trypsin. The degree of inhibition varing in the order: methyl L-lysinate >isopropyl N-benzoyl-L-lysinate > methyl N-tosyl-L-arginate. The inhibition of the hydrolysis of methyl L-lysinate by hexyl [epsilon]-aminocaproate is competitive. [epsilon]-Amino-caproyl- [epsilon] -aminocaproic acid and ethyl [epsilon]-aminocaproyl-[epsilon] -aminocaproate inhibit the caseinolytic, amidase and esterase activities slightly. N,N[image]-Dicarbobenzoxy-L-lysine strongly inhibits the caseinolytic activity, its effect being similar to that of picric acid. The relationship between the inhibitory effects of various derivatives of L-lysine and [epsilon]-aminocaproic acid on the action of trypsin and their molecular structures is discussed on the bases of the results.