Lipoprotein lipase-catalyzed hydrolysis of tri[14C]oleoylglycerol in a phospholipid interface. A monolayer study.
The lipoprotein lipase-catalyzed hydrolysis of triacylglycerol was determined in a lipid monolayer containing egg phosphatidylcholine and tri[14C]oleoylglycerol. In the presence of purified bovine milk lipoprotein lipase and fatty acid-free albumin, the rate of hydrolysis of tri[14C]oleoylglycerol, as determined by the decrease in surface activity, was dependent upon enzyme concentration and was enhanced by the addition of apolipoprotein C-II, the activator protein for the enzyme. Increasing the triacylglycerol content of the phospholipid monolayer from 1 to 6 mol% (relative to phospholipid) enhanced the rate of catalysis in the presence and absence of apolipoprotein C-II. However, at low substrate concentrations (less than 4 mol% tri[14C]oleoylglycerol), the activation factor for apolipoprotein C-II was greater than at high (4-6 mol%) triacylglycerol concentrations. The addition of sphingomyelin to the phosphatidylcholine monolayer decreased lipoprotein lipase activity. Based on these monolayer studies, we conclude that lipoprotein lipase catalyzes the hydrolysis of triacylglycerol at a phospholipid interface and that the rate of catalysis is dependent on the lipid composition of the monolayer.
D000818:Animals; D053304:Apolipoprotein C-II; D001053:Apolipoproteins / Q000097:blood; D001056:Apolipoproteins C; D002250:Carbon Radioisotopes; D002417:Cattle; D004789:Enzyme Activation; D005260:Female; D006801:Humans; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008081:Liposomes; D008892:Milk / Q000201:enzymology; D010713:Phosphatidylcholines; D012710:Serum Albumin, Bovine; D014304:Triolein / Q000378:metabolism*
D053304:Apolipoprotein C-II; D001053:Apolipoproteins; D001056:Apolipoproteins C; D002250:Carbon Radioisotopes; D008081:Liposomes; D010713:Phosphatidylcholines; D014304:Triolein; D012710:Serum Albumin, Bovine; D008071:Lipoprotein Lipase