Key enzyme in triglyceride metabolism. Catalyzes the hydrolysis of triglycerides from circulating chylomicrons and very low density lipoproteins (VLDL), and thereby plays an important role in lipid clearance from the blood stream, lipid utilization and storage (PubMed:8675619). Although it has both phospholipase and triglyceride lipase activities it is primarily a triglyceride lipase with low but detectable phospholipase activity (By similarity). Mediates margination of triglyceride-rich lipoprotein particles in capillaries (PubMed:24726386). Recruited to its site of action on vascular endothelium by binding to GPIHBP1 and cell surface heparan sulfate proteoglycans (PubMed:20620994, PubMed:24726386, PubMed:27811232). a triacylglycerol + H2O = a diacylglycerol + a fatty acid + H(+) a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 2-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) 1,2,3-tri-(9Z-octadecenoyl)-glycerol + H2O = (9Z)-octadecenoate + di-(9Z)-octadecenoylglycerol + H(+) 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphocholine + H2O = (9Z)-octadecenoate + (9Z-octadecenoyl)-sn-glycero-3-phosphocholine + H(+) 1,2,3-tributanoylglycerol + H2O = butanoate + dibutanoylglycerol + H(+) 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine + H2O = H(+) + hexadecanoate + hexadecanoyl-sn-glycero-3-phosphocholine The apolipoprotein APOC2 acts as a coactivator of LPL activity (By similarity). Ca(2+) binding promotes protein stability and formation of the active homodimer. Interaction with GPIHBP1 protects LPL against inactivation by ANGPTL4 (By similarity). Homodimer (PubMed:25066055). Interacts with GPIHBP1 with 1:1 stoichiometry (PubMed:17403372, PubMed:20620994, PubMed:24726386). Interacts with APOC2; the interaction activates LPL activity in the presence of lipids (By similarity). Interaction with heparan sulfate proteoglycans is required to protect LPL against loss of activity. Associates with lipoprotein particles in blood plasma (By similarity). Interacts with LMF1 and SEL1L; interaction with SEL1L is required to prevent aggregation of newly synthesized LPL in the endoplasmic reticulum (ER), and for normal export of LPL from the ER to the extracellular space (PubMed:25066055). Interacts with SORL1; SORL1 acts as a sorting receptor, promoting LPL localization to endosomes and later to lysosomes, leading to degradation of newly synthesized LPL (By similarity). Newly synthesized LPL binds to cell surface heparan proteoglycans and is then released by heparanase. Subsequently, it becomes attached to heparan proteoglycan on endothelial cells (PubMed:27811232). Locates to the plasma membrane of microvilli of hepatocytes with triglyceride-rich lipoproteins (TRL). Some of the bound LPL is then internalized and located inside non-coated endocytic vesicles (By similarity). Detected in white and brown adipose tissue and heart muscle, especially at the lumenal surface of capillaries (PubMed:25066055, PubMed:27811232, PubMed:20620994). Detected on capillary endothelium in the lactating mammary gland (PubMed:27811232). Detected in blood plasma (at protein level) (PubMed:17403372, PubMed:25066055). Expressed in liver, epididymal fat, heart, psoas muscle, lactating mammary gland, adrenal, lung, and ovary. Highest levels in heart and adrenal gland. Maximum expression in adipose tissue during early development. In heart, low levels 6 days before birth increasing 278-fold as animals reach adulthood. Tyrosine nitration after lipopolysaccharide (LPS) challenge down-regulates the lipase activity. N-glycosylated. Mice are born at the expected Mendelian rate. At birth, mutant pups have threefold higher plasma triglyceride levels and sevenfold higher VLDL cholesterol levels relative to wild-type. After suckling they become progressively pale, then cyanotic, and die at about 18 hours after birth. At 18 hours after birth, their plasma triglyceride levels reach 15'090 mg/dl, compared to 188 mg/dl for wild-type. At the same time point, VLDL cholesterol levels reach 280 mg/dl in mutant pups, compared to 6 mg/dl in wild-type. Mutant pups show severly reduced adipose tissue, and their livers are deficient in intracellular lipid droplets. Likewise, the numbers of intracellular lipid droplets in skeletal muscle are severely reduced. Lungs display lipid-filled alveoli and dilated capillaries that are engorged with lipoprotein particles. These particles are marginated and seem to block the access of red blood cells to the vascular endothelium. Belongs to the AB hydrolase superfamily. Lipase family.