STABILITY OF HYDROLYTIC ENZYMES IN WATER-ORGANIC SOLVENT SYSTEMS

The effects of organic solvents on the stabilities of bovine pancreas trypsin. chymotrypsin, carboxypeptidase A and porcine pancreas lipase were studied. Water-miscible solvents (ethanol, acetonitrile, 1,4-diox ane and dimethyl sulfoxide) and water-immiscible solvents (ethyl aceta te and toluene) were used in 100 mM phosphate buffer (pH 7.0) or 100 m M Tris/KCl buffer (pH 7.0) in concentrations of 20-80% (v/v). All hydr olytic enzymes studied were inactivated by mixtures containing dimethy l sulfoxide at higher concentrations. Trypsin and carboxypeptidase A r esisted solvent mixtures containing acetonitrile, 1,4-dioxane and etha nol. They preserved more than 80% of their starting activities during 20-min incubations. The activities of lipase and chymotrypsin decrease d with increasing concentration of water-miscible polar organic solven ts, but at higher concentrations (80%) 70-90% of the activity remained . In mixtures with water-immiscible solvents, the decrease in activity of carboxypeptidase A was pronounced. Trypsin and chymotrypsin underw ent practically no loss in activity in the presence of toluene or ethy l acetate. In respect of stability, the polar solvent proved to be mor e favorable for lipase. These results suggest that the conformational stabilities of hydrolytic enzymes are highly dependent on the solvent- protein interactions and the enzyme structure. (C) 1998 Elsevier Scien ce B.V.