Influence of Water-Miscible Aprotic Solvents on α-Chymotrypsin Stability

The influence of five different water‐miscible aprotic solvents (dimethyl sulfoxide, dimethylformamide, acetonitrile, acetone, and tetrahydrofuran) on the stability of immobilized α‐chymotrypsin adsorbed onto Celite, has been studied. In all cases, α‐chymotrypsin exhibited non‐first‐order deactivation kinetics, which were adequately analyzed by a two‐step series‐type deactivation model. The main effects of solvents were observed in the first‐step of the kinetic mechanism. The most hydrophilic solvent (DMSO) enhanced greatly the enzyme stability, while the increase in solvent hydrophobicity determines a loss in their protective effect. For the most assayed hydrophobic solvent (THF) a denaturative effect was always showed. These facts were also observed from the analysis of the evolution of the half‐live of the enzyme, as a function of the solvent concentrations and the water distribution between both the macro‐ and microenvironment of the enzyme.