Stabilization of acid phosphatase in DDDACl/n-butyl acetate reverse micelles

Storage stability of acid phosphatase entrapped in reverse micelles was stu died. Supramolecular systems were prepared with a cationic twin chain surfa ctant, didodecyldimethylammonium chloride (DDDAC1), n-butyl acetate as an o rganic solvent and different water percentages. The rate of enzyme deactiva tion was monitored in the temperature interval from 20 to 45 degrees C, at bulk pH from 4.8 to 6.4, either unstirred conditions or under convective mi xing from 250 to 750 rev min(-1), water-to-surfactant molar ratio (w(0)) eq ual to 11.4, 12.7, 14.2 and with the following buffers, Na-citrate, Li-citr ate, K-citrate, Na-propionate. Acid phosphatase entrapped in buffer pools o f reverse micelles exhibited enhanced stability in comparison with the enzy me in the pure aqueous phase. Half-life was up to 4 times larger. Both the chemicals used for buffer preparation and buffer pH change, within one unit , were found to influence the rate of acid phosphatase deactivation. The ac tivation energy of enzyme deactivation process in micellar systems was slig htly increasing with w(0) but the values were not very different from the o ne in aqueous phase (145.3 kJ mol(-1)). The rate of deactivation of enzyme confined in the micelles when shear stress was applied was reduced in compa rison with that of the free protein, even though the percentage loss was gr eater.