EFFECTS OF HIGH-PRESSURE ON PAPAIN ACTIVITY AND STRUCTURE

Papain was progressively inactivated by increasing pressures in both p hosphate (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. T hese losses at 800 MPa were more marked when pressure treatment was at 60 degrees C than when at 20 degrees C. Even though inactivation occu rred at 800 MPa, electrophoretic and calorimetric analysis indicated t here was little change in size or conformation of the enzyme. The loss in activity, though, was very dependent on the oxygen concentration d uring pressure treatment, and it is suggested that oxidation of the th iolate ion at the active site, to SO2- or SO3-, is the major reason fo r the pressure inactivation of papain.