Activation of the phospholipase A1 activity of lipoprotein lipase by apoprotein C-II

The effect of apo very low density lipoprotein (apo VLDL) and apoprotein C-II on the phospholipase A₁ activity associated with lipoprotein lipase (E.C.3.1.1.3) was studied using purified bovine milk lipoprotein lipase. The enzyme degraded¹⁴C phosphatidylcholine (PC) to¹⁴C 2-acyl lysophosphatidylcholine at a rate of 0.28±0.01 nmol/min/ml and triolein at a rate of 20.3±0.4 nmol/min/ml in mixed emulsions of PC and triolein. The phospholipase activity and triacylglycerol lipase activity were both increased by the addition of apo VLDL and apoprotein C-II. After maximal activation, the rate of PC degradation was 1.19±0.02 nmol/min/ml and triolein degradation 64.4±0.4 nmol/min/ml. Activation of phospholipase A₁ activity and triacylglycerol lipase activity occurred in parallel.