lipase (lĪˈpās) [key], any enzyme capable of degrading lipid molecules. The bulk of dietary lipids are a class called triacylglycerols and are attacked by lipases to yield simple fatty acids and glycerol, molecules which can permeate the membranes of the stomach and small intestine for use by the body. Gastric lipase, secreted by the stomach lining, has a p H value for optimal activity around neutrality and would appear, therefore, to be essentially inactive in the strongly acid environment of the stomach. It is suggested that this enzyme is more important for infant digestion since the gastric p H in infancy is much less acid than later in life. Most lipid digestion in the adult occurs in the upper loop of the small intestine and is accomplished by a lipase secreted by the pancreas. Phospholipases are the enzymes that degrade phospholipids.