Purification and Properties of Pancreatic Juice Cholesterol Esterase

Abstract

Rat pancreatic juice cholesterol ester hydrolase (EC 3.1.1.13) has been purified 600-fold by sequential precipitation with 35% acetone, diethylaminoethyl cellulose chromatography, and hydroxylapatite chromatography. The purified enzyme gives a single band on polyacrylamide disc electrophoresis and will not hydrolyze methyl butyrate, triolein, or secondary alcohol esters. Data are presented that strongly suggest that the cholesterol ester-synthesizing and -hydrolyzing activities in pancreatic juice are a function of the same enzyme. The pH optima are 6.2 for synthesis and pH 6.6 for hydrolysis of cholesterol esters. Using an equimolar mixture of fatty acids, the relative rates of cholesterol ester formation were oleate, 100; linoleate, 71; palmitate, 56; stearate, 43; and laurate, 11. For cholesterol ester hydrolysis, with a micellar substrate system, the rates were oleate, 100; palmitate, 107; stearate, 104; and linoleate, 55. Data are also presented on the effects of ions and inhibitors, and on the cofactor function of bile salts in the enzymatic reaction.