PURIFICATION AND IDENTIFICATION OF 2 DISTINCT ISOFORMS OF RABBIT PANCREATIC CHOLESTEROL ESTERASE

Cholesterol esterase (CEases; E.C. 3.1.13) has been purified to homoge neity from rabbit pancreas. The method of purification consists of hom ogenization of total pancreas, high speed centrifugation, anion exchan ge column chromatography on S-Sepharose, size exclusion on Sephacryl f ollowed by affinity chromatography on heparin agarose. During the puri fication procedure, two distinct isoforms of CEases have been identifi ed. Both forms are similar in their molecular weights, bile salt requi rement and pH optima but differ in their sensitivity to heparin. Isofo rm-I is resistant and isoform-II is sensitive to heparin. In the norma l pancreas of the adult rabbit, the amount of each of the enzymes appe ars to be in equimolar concentrations. Physiological significance of t he existence of heparin sensitive and resistant forms by the same tiss ue is unclear. In view of the significant role played by heparin in th e modulation of CEase activity and several other physiological functio ns, these two isoforms may have different mechanisms of action on the hydrolysis of carboxyl esters of cholesterol and vitamins.