Modulation of enzymatic activity by aqueous two-phase systems and pressure - rivalry between kinetic constants.

We studied the combined effects of an aqueous two-phase system (ATPS) invoking liquid-liquid phase separation and pressure on an enzymatic hydrolysis reaction. We show that simple steric crowding effects are not able to explain the kinetic constants and their pressure dependence in the ATPS. Additional contributions, such as changes in water activity and non-specific weak interactions with ATPS components have to be invoked to explain the results obtained. The findings are relevant for understanding cellular processes of piezophiles and might have significant bearings on biotechnological applications using liquid-liquid phase separation and pressure in concert for modulating enzymatic reactions.