Otherwise known as triacylglycerol acylhydrolases, Lipase enzymes are defined as any enzyme that serves as a catalyst in the hydrolysis of lipids fats, and are found as a subclass of the esterases.
Built on an alpha/beta hydrolase fold, they use a chymotrypsin-like hydrolysis mechanism courtesy of a catalytic triad of a histidine base, serine nucleophile, and acid residue.
Lipase enzymes are found in an array of living organisms. As far as human biology is concerned, they are primarily associated with the digestive system. Both the pancreatic lipase (PL) and pancreatic lipase related protein 2 (PLRP2) are secreted by the pancreas while the hepatic lipase, endothelial lipase, and lipoprotein lipase also function within the gut.
Not all lipases are found in the gut, though. For example, the lingual lipase is secreted by the Ebner's glands located at the back of the tongue as well as other salivary glands including the sublingual glands and the parotid glands. Their impact on digestion is crucial while blood tests focused on the lipase levels can help identify conditions such as acute pancreatitis.
Lipase enzymes can be found in the blood, gastric juices, pancreatic secretions, intestinal juices, and adipose tissues functioning to hydrolyse triglycerides (fats) into their component fatty acid and glycerol molecules.
Lipase digestion begins when bile salts lower the surface tension of the fat droplets within the lumen of the small intestine, allowing lipases to attack triglyceride molecules. Fatty acids and glycerol molecules are then transported through the epithelial cells of the intestine wall before being resynthesizsed into triglycerides. They are then transported to muscles and tissues to hydrolyse the triglycerides.
Lipases break down the triglycerides, enabling fatty acids to reenter the bloodstream, promoting the transport to the tissues that need the energy from those fats. Lipases can, therefore, be used by the body in a diverse range of biological processes such as dietary triglycerides, cell signaling, and inflammation. They can be secreted to extracellular spaces, breaking down the molecules into solutions that can be easily absorbed and transported throughout the body.
Different lipase enzymes serve different functions. For example, the gastric lipase targets butterfat by stimulating the bile that is activated by the gallbladder when we eat fats.