Enzymatic properties of polyethylene glycol-modified cholesterol esterase in organic solvents.

The solvent dependency and substrate specificity of polyethylene glycol (PEG)-modified cholesterol esterase (CEH) catalyzing cholesterol ester synthesis in organic solvents were studied. When cholesterol and linoleic acid were used as the substrates, PEG-modified CEH synthesized cholesterol linoleate only in water-immiscible organic solvents. Among some solvents capable of solubilizing all of the reaction components (PEG-modified CEH, cholesterol, and linoleic acid), chloroform was most suitable for enzymatic cholesterol linoleate synthesis, and the synthetic activity for cholesterol linoleate decreased in the order chloroform, benzene, toluene, and cyclohexane. PEG-modified CEH synthesized various cholesterol esters with significant substrate specificity. The substrate specificity for cholesterol ester synthesis in benzene was analogous to that for cholesterol ester hydrolysis in aqueous solution.