Protease-catalyzed synthetic reactions and immobilization-activation of the enzymes in hydrophilic organic solvents.

The catalytic feature of serine proteases for synthetic reactions in hydrophilic organic solvents and effects of immobilization by complexation with polysaccharides are described. Free alpha-chymotrypsin and subtilisin Carlsberg catalyze esterification, transesterification, and peptide synthesis in hydro-organic cosolvents with less than 10% water. Subtilisin BPN' is catalytically less active. The medium effects on the reaction kinetics and product yield were investigated in terms of the nature of solvent and water content in the reaction systems. The substrate- and stereo-specificities of the enzymes suggest that the enzymes maintain their native conformations in these low-water organic solvents. The catalytic activities of the proteases markedly increase by immobilization or complexation with polysaccharides, such as chitin or chitosan. The results of the rate measurements suggest that the primary role of the support materials is the activation of the enzymes and the increase in substrate concentration at reaction sites.