Purification and Characterization of Rat Lingual Lipase

Lingual lipase was highly purified from serous glands of rat tongue. Protein containing lipolytic activity was precipitated with 30-60% saturated ammonium sulfate from the 100,000 X g supernatant of a homogenate of the glands, resuspended in buffered solution, treated and precipitated with acetone at -20 degrees C, and redissolved in buffered solution at pH 5.4. This protein was further purified by hydrophobic chromatography on ethyl agarose; it was eluted with a micellar solution of sodium taurodeoxycholate, oleic acid, and monooleoylglycerol at pH 6.3. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed this fraction consisted of one major protein band, with Mr = 51,000, and several minor bands. A similar value for Mr of protein with lipolytic activity was obtained when acetone-precipitated protein was subjected to gel filtration on Sephadex G-200 indicating that 51,000 is the Mr of an active form of lingual lipase. Lingual lipase purified from rat tongue had a specific activity of 230 units/mg of protein (unit = micromoles of fatty acid formed/min at 37 degrees C). Purified lingual lipase hydrolyzed immediately long chain triacylglycerol to diacylglycerol and fatty acid in medium containing 17 mM sodium taurodeoxycholate and 3.3 mM CaCl2 at pH 5.4. It then hydrolyzed diacylglycerol, and later monoacylglycerol, but at rates 1:6 and 1:20, respectively, of that for triacylglycerol. The activity of lingual lipase in the presence of sodium taurodeoxycholate and CaCl2 was decreased only 33% when pH of the incubation medium was increased to 6.5. This indicates that lingual lipase, which is known to be active in stomach, could act in the small intestines.