EFFECT OF HIGH HYDROSTATIC-PRESSURE ON THE ENZYMATIC-HYDROLYSIS OF BETA-LACTOGLOBULIN-B BY TRYPSIN, THERMOLYSIN AND PEPSIN

Hydrolysis of beta-lactoglobulin B (beta-lg B) by pepsin, a process do w at ambient conditions, is facilitated at a moderately high hydrostat ic pressure such as 300 MPa, corresponding to an apparent volume of ac tivation Delta V-# = - 63 ml mol(-1) at pH 2.5, 30 degrees C and Gamma /2 = 0.16. Digestion of beta-lg by trypsin and thermolysin is likewise enhanced by pressure, and the pressure effect has been traced to pres sure denaturation of beta-lg B, which by high-pressure fluorescence sp ectroscopy has been shown to have a large negative volume of reaction, Delta V-o = -98 ml mol(-1), at pH 6.7, 30 degrees C and Gamma/2 = 0.1 6. Pressure denaturation is only slowly reversed following release of pressure and the enhanced digestibility is maintained at ambient press ure for several hours.