Lipases (a synonym for steapsin) are enzymes that split off the neutral fats (triglycerides) of the fatty acid molecule to form di-, monoglycerides and free glycerin.
The main source of lipases that break down food fats is the outer secret of the pancreas. A small amount of lipases is also secreted by the mucosa of the small intestine. The optimum pH of these lipases lies between 7 and 8, i.e., corresponds to the pH of the secretion of the upper parts of the small intestine. Their activity is significantly increased in the presence of cations of Ca2 +, Mg2 +, bile salts and many other factors that increase the degree of emulsification of fats in the intestine. In the stomach, a small activity of lipases is found only in infants, and the optimum of the action of the gastric lipase, in contrast to the lipase of the pancreas and intestine, lies at pH = 5. Some lipase activity, sometimes found in the gastric juices of adults, appears to be due to the lipase of intestinal juice being thrown into the stomach.
The action of lipases is reversible, and already in intestinal juice there is a partial resynthesis from the products of the decomposition of fats of mono- and diglycerides. With a high intensity, the resynthesis of fats takes place in the intestinal wall, and therefore only a small amount of free fatty acids enter the blood from the intestine. The activity of lipases of various organs varies in significant limits and is most pronounced in the liver, lungs and adipose tissue. In the blood, normal activity of lipases is low, but it increases sharply in acute pancreatitis, with necrotic processes in the liver and lungs. In acute pancreatitis, lipase, penetrating from the pancreas into the blood, can cause a significant splitting of fats in fatty tissues and their necrosis.
Increased lipase activity in the blood in acute pancreatitis is observed for a fairly long period (2-3 weeks); therefore, its definition more reliably confirms the diagnosis of acute pancreatitis than the determination of blood diastase. An increase in the lipase content in the blood is usually accompanied by a significant increase in its excretion in the urine. See also Digestion, Enzymes.