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Olivecrona T: [The great Scandinavian Medical Jahre Prize 1994. Nord Med. 1995;110(1):4-8.
Role of lipoprotein lipase in lipoprotein metabolism]. Each day more than 150 g of triglycerides are transported from the intestine in chylomicrons and from the liver in VLDL. The triglycerides are hydrolyzed by lipoprotein lipase at the vascular endothelium in extrahepatic tissues. This releases fatty acids and monoglycerides which can move across aqueous barriers and cell membranes to reach metabolic sites in tissue cells. At the endothelial cell the enzyme is anchored to heparin sulfate proteoglycans. The enzyme is located in a position where it can freely interact with lipoproteins from the circulating blood. The hydrolysis is a rapid and efficient process. A chylomicron containing more than a million triglyceride molecules can be unloaded in less than 10 minutes. As a consequence of triglyceride hydrolysis the lipoproteins are reduced to remnant particles. Some of these are rapidly removed from plasma but some are remodeled into LDL and HDL, lipoproteins that are catabolized slowly and therefore dominate in plasma. The activity of LPL is regulated in a tissue-specific manner and this directs the destination of triglyceride transport. The enzyme binds fatty acids which provides a mechanism for product control of the reaction. When the tissue can no longer assimilate the fatty acids, the lipase reaction is stopped and the lipoprotein returns to the circulating blood. In addition to its catalytic action, lipoprotein lipase can also serve as a ligand for binding of lipoproteins to cell surfaces and to receptors. Hence, the lipase has a dual role in lipoprotein metabolism, mediating both unloading of triglycerides in extrahepatic tissues and particle catabolism in the liver. |
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