ABSTRACT
This chapter describes the chemical or physical modifications of enzymes as the most promising method for stabilization and activation of enzymes in organic solvents. It focuses on enzymes modified either chemically or physically, including enzyme complexes and immobilized enzymes in organic solvents. Organic solvents may be competitive inhibitors of enzymes through specific interactions with enzymes. They may change dissociation states of polar groups on the surface of enzymes. poly(ethylene glycol) (PEG) is an amphiphilic polymer, which is soluble both in water and organic solvents, and this may be responsible for the solubilization of PEG-modified enzymes in both aqueous and nonaqueous media. The aminolysis reaction by PEG-modified papain in organic solvents was applied to the synthesis of a derivative of a salty peptide, ornithyl-ß-alanine. The immobilized enzymes are stable and catalyze esterification, transesterification, and peptide synthesis in hydrophilic organic solvents.
