Effects of high pressure on papain activity and structure

Abstract

Papain was progressively inactivated by increasing pressures in both phosphate (pH 5·0 and 6·8) and Tris (pH 6·8) buffer, but in all systems the effect at pressures up to 600 MPa was minimal and independent of the temperature. However, at 800 MPa, significant losses were found. These losses at 800 MPa were more marked when pressure treatment was at 60°C than when at 20°C. Even though inactivation occurred at 800 MPa, electrophoretic and calorimetric analysis indicated there was little change in size or conformation of the enzyme. The loss in activity, though, was very dependent on the oxygen concentration during pressure treatment, and it is suggested that oxidation of the thiolate ion at the active site, to SO2− or SO3−, is the major reason for the pressure inactivation of papain. © 1997 SCI.