Human postheparin plasma hepatic lipase activity against triacylglycerol and phospholipid substrates

Recent evidence has suggested that the major physiological substrate of the heparin-releasable (postheparin plasma) hepatic lipase is HDL2-phospholipid. However, all the current assay methods for this enzyme are based on the use of triacylglycerol substrate. Even though both lipolytic activities of hepatic lipase are likely to be due to a single enzyme it is possible that the use of unphysiological lipid as a substrate may give misleading results. Therefore we did parallel assays of the activity of postheparin plasma hepatic lipase using triacylglycerol, monoacylglycerol and phospholipid substrates. The correlation coefficients between the three lipolytic activities were 0.95-0.98, indicating that identical results are obtained using any of these three lipids in the assay of postheparin plasma hepatic lipase.