The Role of Water in the Dissociation of Enolase, a Dimeric Enzyme

Abstract

Exposure of enolase to hydrostatic pressure results in a reversible inactivation of the enzyme; increasing the osmotic pressure, by adding glycerol, glucose, or sucrose to the solutions stabilizes the enzyme against the effects of hydrostatic pressure. The effects of both hydrostatic and osmotic pressure on the rate of inactivation have been determined. As hydrostatic pressure increases, the rate of inactivation increases. As osmotic pressure increases, the rate of inactivation decreases. We have interpreted these results using the following model: hydrostatic pressure causes the active, dimeric enzyme to dissociate into inactive monomers; during the dissociation, the subunit interfaces become hydrated. As osmotic pressure increases, hydration becomes more difficult and dissociation is reduced. The combined effects of hydrostatic and osmotic pressure suggest that much of this hydration occurs during formation of the transition state.