CATALYTIC ACTIVITY OF THERMOLYSIN UNDER EXTREMES OF PRESSURE AND TEMPERATURE - MODULATION BY METAL-IONS

The catalytic activity of thermolysin (TL), a Zn-dependent neutral pro tease from Bacillus thermoproteolyticus, has been studied over a wide interval of pressures (1 bar to 4 kbar) and temperatures (20 degrees C to 80 degrees C) by monitoring hydrolysis of a low-molecular-mass sub strate, 3-(2-furylacryloyl)-glycyl-L-leucine amide. This reaction show s a very large negative value for the activation volume and, because o f that, simultaneous increase in temperature and pressure leads to a s ignificant (up to 40-fold) acceleration of the reaction. At pressures higher than 2-2.5 kbar, the reaction rate starts to decrease due to di sactivation of TL. This disactivation is explained in part by pressure -promoted dissociation of zinc ion from the active site and can be inh ibited by adding exogenous zinc. Thus, this thermostable protease does not specifically show a higher stability at high pressure in comparis on with small mesophilic proteases, (C) 1998 Elsevier Science B.V. All rights reserved.