Thrombin-catalyzed hydrolysis of p-nitrophenyl esters

Abstract

A series of p-nitrophenyl esters, whose rates of basic hydrolysis varied over 100-fold, were synthesized. The thrombin-catalyzed hydrolysis did not follow the relative order of the non-enzymic breakdown of these substrates, but it showed a range of turnovers of about 2500-fold in going from p-nitrophenyl acetate through acetylglycinate, iodoacetate, acetyl- l-leucinate, carbobenzoxyglycinate to carbobenzoxy- l-phenylalaninate and carbobenzoxy- l-tyrosinate. The latter two compounds are as good thrombin substrates as N α-p -tosyl- l-arginine methyl ester. It is concluded that the presence of an apolar phenyl side chain in the substrate molecule plays an important part in promoting its hydrolysis by the enzyme.