The separation of human serum high density lipoproteins by hydroxyapatite column chromatography

Abstract

Human serum high density lipoprotein subfractions 2 and 3, isolated by preparative ultracentrifugation after blocking the enzyme phosphatidylcholine: cholesterol acyl transferase, have been subfractionated further by hydroxyapatite column chromatography. From subfraction 2 we reproducibly obtained 5 and from subfraction 3, 6 fractions differing in chemical compositon and apolipoprotein content. The fractions eluting at low salt concentrations were composed primarily of apolipoprotein-A polypeptides while those eluting at high salt concentrations consisted primarily of apolipoprotein-C. From all the 11 subfractions only one contained the “arginine-rich” polypeptide. The apolipoprotein-C-containing fractions were richer in triacylglycerol, phospholipids and free cholesterol as compared to the apolipoprotein-A-containing ones. Although small differences of their partial specific volumes existed, the obtained values indicate that all subfractions belonged to the parent density class. The implications of these results to the current view of lipoprotein metabolism are discussed.