Bovine cathepsin D activity under high pressure

The stability and catalytic activity of bovine cathepsin D in Bis-Tris buffer (pH 6.0) in different pressure-temperature domains (0.1-650 MPa, 20-75 degrees C) were investigated and described with mathematical models. Cathepsin D inactivation followed first-order kinetics at all pressure-temperature conditions tested. The protease was largely pressure stable at room temperature and heat stable at ambient pressure up to 300 MPa and 55 degrees C, respectively, causing less than 10% inactivation after 10 min treatment. Pressure and temperature act synergistically on the enzyme inactivation under most conditions. However, at 100 MPa a significant stabilisation of the enzyme against temperature-induced inactivation was observed. Pressure drastically inhibited the cleavage of a synthetic substrate by cathepsin D in Bis-Tris buffer (pH 6.0) causing a reduction of the catalytic rate of more than 50% at 100-400 MPa. Maximal substrate cleavage by cathepsin D was identified at 60 degrees C and ambient pressure conditions after 20 min treatment. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.