Rat Lingual Lipase

The lingual serous glands of rat tongue secrete a potent lipase that hydrolyzes long chain triglycerides. The characteristics of this lipase were studied in preparations of lingual glands from Sprague-Dawley rats. Lipase activity was measured by the release of free fatty acids from emulsified tri[3H]oleate. Lipase activity in the 100,000 x g supernatant of lingual serous gland homogenate was excluded from Sephadex G-200 indicating a molecular weight >500,000. Acetone treatment of the 100,000 x g supernatant led to complete conversion to a low molecular weight (45,000) unit. Lipolytic activity in the absence of fatty acid acceptor (albumin) had a broad pH optimum range (2.2 to 6.0) and formed mainly partial glycerides and free fatty acids. Addition of excess albumin (0.7 to 1.4 mM) stimulated lipolysis (lOO%), led to the complete hydrolysis of triglycerides to glycerol and free fatty acids, and restricted the pH optimum to 4.5 to 5.5. The data show that lingual lipase differs from pancreatic lipase, but closely resembles the lipolytic activity in human gastric juice. Because lingual lipase is acid-resistant, has a low pH optimum, and does not require bile salts, it can act in the stomach where it initiates the hydrolysis of dietary fat. Intragastric lipolysis is probably of major importance in physiological and pathological conditions that are associated with low pancreatic lipase levels, such as prematurity or congenital absence of pancreatic lipase.