Halophilic adaptation of enzymes

It is now clear that the understanding of halophilic adaptation at a molecular level requires a strategy of complementary experiments, combining molecular biology, biochemistry, and cellular approaches with physical chemistry and thermodynamics. In this review, after a discussion of the definition and composition of halophilic enzymes, the: effects of salt on their activity, solubility, and stability are reviewed. We then describe how thermodynamic observations, such as parameters pertaining to solvent-protein interactions or enzyme-unfolding kinetics, depend strongly on solvent composition and reveal the important role played by water and ion binding to halophilic proteins. The three high-resolution crystal structures now available for halophilic proteins are analyzed in terms of haloadaptation, and finally cellular response to salt stress is discussed briefly.