Chylomicron protein content and the rate of lipoprotein lipase activity

Chylomicrons isolated form rat intestinal lymph were incubated with plasma. Protein transfer to chylomicrons, reaction rate with purified lipoprotein lipase, and content of lipase cofactor were determined. While the overall protein content of chylomicrons was increased 3--4-fold, and the content of lipase cofactor increase 4-fold, reaction velocity of the activated particles with lipoprotein lipase was increased only 1.3-fold. Maximal rate of hydrolysis was achieved in the presence of much smaller quantities of activator than the lipoprotein particles were capable of binding, and chylomicrons were fully activated for triclyceride hydrolysis in the presence of only 10% plasma for triglyceride concentrations of up to 3 mg/ml. Cofactor protein was not rate-limiting for hydrolysis of triglyceride from chylomicrons. These results are discussed in the light of recent concepts of the regulation of lipoprotein lipase activity.