Triglyceride lipases () are a family of lipolytic enzymes that hydrolyse ester linkages of triglycerides. Lipases are widely distributed in animals, plants and prokaryotes. At least three tissue-specific isozymes exist in higher vertebrates, pancreatic, hepatic and gastric/lingual. These lipases are closely related to each other and to lipoprotein lipase (), which hydrolyses triglycerides of chylomicrons and very low density lipoproteins (VLDL). The most conserved region in all these proteins is centred on a serine residue which has been shown to participate, with a histidine and an aspartic acid residue, in a charge relay system. Such a region is also present in lipases of prokaryotic origin and in lecithin-cholesterol acyltransferase () (LCAT), which catalyzes fatty acid transfer between phosphatidylcholine and cholesterol. Human pancreatic lipase Pancreatic lipase, also known as pancreatic triacylglycerol lipase or steapsin, is an enzyme secreted from the pancreas. As the primary lipase enzyme that hydrolyzes (breaks down) dietary fat molecules in the human digestive system, it is one of the main digestive enzymes, converting triglyceride substrates like 1 found in ingested oils to monoglycerides 3 and free fatty acids 2a and 2b. Bile salts secreted from the liver and stored in gallbladder are released into the duodenum, where they coat and emulsify large fat droplets into smaller droplets, thus increasing the overall surface area of the fat, which allows the lipase to break apart the fat more effectively. The resulting monomers (2 free fatty acids and one 2-monoacylglycerol) are then moved by way of peristalsis along the small intestine to be absorbed into the lymphatic system by a specialized vessel called a lacteal. Unlike some pancreatic enzymes that are activated by proteolytic cleavage (e.g., trypsinogen), pancreatic lipase is secreted in its final form. However, it becomes efficient only in the presence of colipase in the duodenum. In humans, pancreatic lipase is encoded by the PNLIP gene. Human proteins containing this domain LIPC LIPG LIPH LIPI LPL PLA1A PNLIP PNLIPRP1 PNLIPRP2 PNLIPRP3 Diagnostic importance Pancreatic lipase is secreted into the duodenum through the duct system of the pancreas. Its concentration in serum is normally very low. Under extreme disruption of pancreatic function, such as pancreatitis or pancreatic adenocarcinoma, the pancreas may begin to autolyse and release pancreatic enzymes including pancreatic lipase into serum. Thus, through measurement of serum concentration of pancreatic lipase, acute pancreatitis can be diagnosed. Inhibitors Lipase inhibitors such as orlistat can be used as a treatment