Determining Lipoprotein Lipase and Hepatic Lipase Activity Using Radiolabeled Substrates

Hepatic lipase (HL) and lipoprotein lipase (LPL) are two lipolytic enzymes that play an important role in the metabolism of circulating lipoproteins. Both enzymes catalyze the esterolysis of fatty acids present at the sn -1 (3) position of triacylglycerols. HL is functional at the lumenal face of liver sinusoids, where it is responsible for the hydrolysis of chylomicrons remnants, IDL and HDL; HL is also present in adrenal cortex and ovary, where it is thought to contribute to HDL cholesterol uptake by these tissues ( 1 ). LPL, located at the capillary endothelium of a number of extra-hepatic tissues, hydrolyzes circulating triglyceride-rich lipoproteins (chylomicrons and VLDL) ( 2 ).