Purification and some properties of a cholesterol esterase from rat liver

A cholesterol esterase operating at a slightly alkaline pH was purified to electrophoretic homogeneity from rat liver cytosol. The enzyme has a molecular weight of 260 000 and is composed of four active subunits of identical molecular weight. The purified enzyme is not able to synthesize cholesteryl esters. Trihydroxy bile salts are absolutely required for the hydrolysis of cholesteryl esters and apparently convert enzyme tetramers into active monomers. They may regulate the esterase activity by maintaining a balance between enzyme monomers and polymers the synthesis of bile acids.