Characterization of a diester lipase activity in human erythrocytes

A diester lipase activity is described in human red blood cells (RBC). Diester lipase activity acts as a membrane-bound enzyme and is assayed using intact RBC as the enzyme source. An emulsion of di-[3H]-oleoylglycerol (0.6 mM) serves as the substrate. The optimum pH for the reaction is 7.8 at 37 degrees C. Lipolytic rates are monitored by quantitation of the amount of [3H]-oleic acid released during 20 min of incubation after a two-step purification procedure. [3H]-oleic acid is first extracted from the incubation mixture by means of a liquid-liquid partition system and further isolated by thin-layer chromatography. Suspensions of purified RBC obtained from 36 healthy adult subjects had a diester lipase activity of 196 +/- (SD) 45 mU/10(12) RBC, with no difference between men and women.