Purified postheparin plasma lipoprotein lipase in primary hyperlipoproteinemias

Abstract

Purified postheparin plasma lipoprotein lipase (LPL) of normolipidemic and primary hyperlipoproteinemic subjects was characterized by lipoprotein C polypeptide activation and specificity for triglycerides in chylomicrons and VLDL. Chromatography of normal LPL on Sephadex G-100 resulted in two protein peaks, LPLC-1 (activated by C-I but not C-II) and LPLC-II (activated by C-II but not C-I). LPL from type I hyperlipoproteinemic subjects was not activated by C-I and C-II activation was reduced to 40% of control. Hydrolysis of chylomicron and VLDL triglycerides was severely impaired. Although chromatography of type I LPL resulted in two protein peaks, the protein peak corresponding to LPLC-I did not exhibit lipolytic activity and LPLC-II was reduced to 50% of control in protein and enzyme specific activity. Type III LPL was normal in respect to LPLC-I while LPLC-II averaged 40% of control. Hydrolysis of chylomicron and VLDL was reduced to 50% and 10% of control, respectively. An etiological implication for LPLC-I and/or LPLC-II in type I and III hyperlipoproteinemias is suggested.