Lipoprotein lipase and hepatic triacylglycerol lipase were partially purified from human post-heparin plasma by heparin-Sepharose affinity chromatography. The activities of both enzymes as well as rat adipose lipoprotein lipase were tested with normal and triacylglycerol-rich lipoproteins from all major density classes. Lipoprotein lipase hydrolyzed the chylomicrons of patients with type 1 hyperlipoproteinemia far more efficiently than did hepatic triacylglycerol lipase, with a ten-fold lower Km and four-fold higher V. Triacylglycerol in very low density lipoproteins was hydrolyzed slower than that in chylomicrons by lipoprotein lipase, whereas hepatic triacylglycerol lipase had much greater activity against very low density lipoproteins than against chylomicrons. Triacylglycerol-rich low density lipoproteins and high density lipoproteins from the plasma of patients with Tangier disease and types 1 and 5 hyperlipoproteinemia were also tested as substrates for these enzymes. Low density lipoproteins, with triacylglycerol contents up to 40% dry weight, were hydrolyzed by both enzymes. Very low density lipoprotein, low density lipoprotein-1 (1.006 < → < 1.035 g/ml), and low density lipoprotein-2 (1.035 < → < 1.063 g/ml) were hydrolyzed by hepatic triacylglycerol lipase at comparable rates. Lipoprotein lipase, however, was more active against very low density lipoprotein than low density lipoprotein-1, and low density lipoprotein-2 was a relatively poor substrate. This pattern of substrate specificity was also exhibited by rat adipose lipoprotein lipase. It is postulated that triacylglycerol enrichment of low density lipoproteins, and low density lipoprotein hydrolysis by lipoprotein lipase or hepatic triacylglycerol lipase may contribute to the low density lipoprotein hypercatabolism characteristic of hypertriglyceridemia. Neither rat adipose lipoprotein lipase nor human post-heparin plasma lipoprotein lipase released fatty acids from high density lipoproteins, even when triacylglycerol accounted for greater than 25% of high density lipoprotein mass. High density lipoprotein triacylglycerol was hydrolyzed to a limited extent by hepatic triacylglycerol lipase, and the fatty acid release was shown not to be due to phospholipase activity. © 1979.
