The Mechanism of Salt Activation of Thermolysin: Relation with Pressure Activation and Implications of Hydration Change Coupled with Rate Process

Thermolysin (E.C. 3.4.24.4) shows a remarkable increase in catalytic activity at elevated salt concentrations or hydrostatic pressures. Salt effected Kcat, only, whilst the effect of pressure was related to both Kcat, and Km. The turnover, derived from kcat/Km(V), of the hydrolysis of an N-acyldipeptide amide substrate was scarcely affected by addition of salt. These results were interpreted in terms of the stabilization of increased (or exposed) charges at the transition state of the reaction.