Serum high-density lipoprotein: effect of change in structure on activity of chicken adipose tissue lipase.

The high-density (1.063 to 1.21 g/ml) lipoprotein in human serum was analyzed as activator for a lipoprotein lipase isolated from chicken adipose tissue. The activating capacity was lost when the lipoprotein was extracted with a mixture of ethanol and ethyl ether (3:2 by volume) at -10 degrees C and it was restored upon incubation of the extracted protein with aqueous sols of either whole phospholipids or the lecithin fraction prepared from the high-density lipoprotein. Since phospholipid sols alone proved ineffective as substrate activators, the complex which forms upon incubation of the extracted lipoprotein with phospholipids appears to be a necessary requirement for lipoprotein lipase activity.