Purification and properties of aortic cholesteryl ester hydrolase

Abstract

The enzyme(s) present in acetonedried powder of rat and rabbit aortas, which catalyzes the synthesis and hydrolysis of cholesteryl ester, was purified partially by acid precipitation, acetone fractionation, O-(diethylaminoethyl) cellulose chromatography, and Sephadex G-100 filtration. The synthetic activity was purified by 120-fold (rat) and 140-fold (rabbit). Purification of hydrolytic activity was 90-fold (rat) and 103-fold (rabbit). Cholesteryl ester hydrolase activity was separated from nonspecific esterase by column chromatography. Both synthetic and the hydrolytic activities are apparently the functions of one enzyme. The mol wt of the enzyme was estimated to be 140,000 dalton as determined by Sephadex G-200 gel filtration. The extracts of the acetone-dried powders of aortas of both species contained an inhibitor of synthetic activity. The inhibitor was nondialyzable and was precipitated at pH 5.7. Both activities were found to be fairly nonspecifc with regard to sterol and fatty acids. With oleic acid, the relative rates of sterol ester synthesis were: cholesterol, 100; cholestanol, 94; desmosterol, 35; coprostanol, 24; ergosterol, 20; and beta-sitosterol, 19. Epicholesterol was not esterified. Oleic acid was most active in cholesteryl ester synthesis, the relative rates being: oleic greater than linoleic greater than arachidonic greater than palmitic greater than stearic greater than butyric. The rate of hydrolysis was maximum with cholesteryl linoleate followed by oleate, linolenate, palmitate, stearate, and laurate in decreasing order.