Bounded water kinetic model of beta-galactosidase in reverse micelles

In the present investigation, beta-galactosidase was solubilized into Aerosol OT (AOT)/isooctane reverse micelles. Kinetic data for the hydrolysis of o-nitrophenyl-beta-D-galactopyranoside (ONPG) at different pH values and molar ratios of water to AOT (Wo) were collected. It was observed that the usual kinetic model used for beta-galactosidase catalysis in aqueous systems failed to represent the experimental data. A bounded water model, however, showed a better correlation between enzymatic activity and Wo. In contrast to the aqueous system, controlling the water concentration in the reverse micelles allows the rate constants for the reaction between water molecules and glycosyl-enzyme complexes to be evaluated.