Tailoring the Microenvironment of Enzymes in Water-Poor Media

Abstract

This chapter summarizes efforts toward the understanding of microenvironmental factors in biocatalysis. The chapter describes some systems that are not yet fully understood. A crucial factor in biocatalysis in organic media is water. A completely dehydrated enzyme is not active. Small amounts of water are needed to activate the enzyme. The distribution of water in the system is of great importance for enzyme catalysis. Some water is dissolved in the solvent, some is bound to the enzyme, and some is bound to the support. It is the amount of water bound to the enzyme that governs its catalytic activity. Many reports in the literature state only the total amount of water present in the system. This makes it difficult to compare the enzymatic activities observed under different conditions, for example, in different solvents, because enzyme hydration (and thereby enzyme activity) is influenced by several parameters. By carrying out enzymatic reactions in organic media at fixed thermodynamic water activity, the effects of the solvent and the support can be studied without interference because of the partitioning of water. The choice of support material is crucial. The third factor to take into consideration when characterizing a system is the protein phase. Besides applying enzymes on solid supports, much effort has been devoted to creating homogeneous systems. Since the protein molecule per se is not soluble different arrangements have been tried.