KINETICS OF ENZYME DEACTIVATION - A CASE-STUDY

Acid phosphatase (EC 3.1.3.2, from potato) thermal deactivation was st udied by kinetic methods with specific reference to the effect of medi um properties. The time-course of activity decay was employed as an in direct probe for analysing the structural changes undergone by the pro tein. The experimental data show convex log(activity) vs. time curves. Usually, departure from simple first-order kinetics is explained by p ostulating enzyme aggregation, or enzyme heterogeneity, or formation o f partially deactivated forms of the enzyme. None of the above models was entirely satisfactory in interpreting the experimental data. The c urrent models for enzyme thermal deactivation therefore appear to be p urely correlative. The effects of medium changes were accounted for on the basis of a phenomenological approach, the 'equivalent temperature ' yielding a monoparametric model.