MODIFICATION EFFECTS OF ORGANIC-SOLVENTS ON MICROENVIRONMENT OF THE ENZYME IN THERMOLYSIN-CATALYZED PEPTIDE-SYNTHESIS OF N-(BENZYLOXYCARBONYL)-L-PHENYLALANYL-L-PHENYLALANINE METHYL-ESTER

Thermolysin-catalyzed peptide synthesis using N-(benzyloxycarbonyl)-L-phenylalanine (Z-Phe) and L-phenylalanine methyl ester (Phe-OMe) as substrates was done mainly in a water-organic one phase solvent system. The organic solvent content used was less than the saturation concentration in buffer. With organic solvents with high log P values, the enzymatic activity increased as the organic solvent content increased; but further increases in the organic solvent content decreased the enzymatic activity, showing an ''organic activity''' profile. On the other hand, with organic solvents of low log P values, the enzymatic reaction was inhibited even by the initial addition of organic solvents. When a correlation between maximum activities and log P values or Hildebrand solubility parameters was investigated, a linear correlation was obtained among the same category of organic solvents, but not between categories. This suggests that the direct effect of organic solvents on the microenvironment of the enzyme largely depends on the molecular structure of the solvents.