Essential water is very important fot the enzyme to keep its bioactivity in organic solvents. The effect of free water content on the synthesis of Z-Tyr-Gly-Gly-OEt and Z-Tyr-Gly-NHNHPh by α- chymotrypsin and Boc-Phe-Ala-NHNHPh by thermoase in various organic solvents, including dichloromethane, cyclohexane, ethyl acetate and toluene, was investigated. By replacing free water with salt hydrates such as Na2SO4·10H2O or Na2CO3·10H2O, the effect of salt hydrates on the above reaction systems was also discussed. The results indicated that essential water can be supplied by slat hydrates, and water activity (αw) of the synthetic reaction system can also be fixed by salt hydrates, both favoring the formation of peptide bonds.

Key words: TRYPSIN, OLIGOPEPTIDE, SODIUM SULFATE, HYDRATE, HYDROLASE, PROTEOLYSIS