[Effect of temperature on the hydrolysis of some synthetic substrates by thrombin and trypsin].

The effect o temperature on the thrombin- and trypsin-catalyzed hydrolysis of N(alpha)-arylsulfonyl-L-arginine methyl esters (I) and N(alpha)-methoxyphenylsulfonyl-L-valyl-L-arginine methyl ester (II) at pH 8.5 was studied. The non-linearity of the Arrhenius plots of the rate constants for thrombin can be due to changes in the rate-limiting step of the enzymatic reaction. The activation parameters delta G not equal to, delta H not equal to, delta S not equal to were determined. It was shown for both thrombin and trypsin that unfavourable alterations of the entropy of activation decreased with a transition from the substrates (I) to compound II. It was assumed that the low efficiency of hydrolysis of synthetic substrate by thrombin is probably caused by the lack of conformation changes in the enzyme active site, which is probably necessary for a specific catalysis by thrombin.