Lipolytic activity of California-laurel (Umbellularia californica) seeds

The lipid content of dormant mature seeds of the California-laurel (Umbellu laria californica) was 74% (mass basis) and decreased upon germination, rea ching 43% 5 wk after germination. Dormant seeds contained only barely detec table lipase activity. Lipase activity rose upon germination, peaking 2 to 3 wk after the onset of visible germination. The combined addition of three detergents, 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate (1 mM), taurocholic acid (1 mM), and Tween-20 (0.05%, vol/vol) during homogeni zation increased the lipolytic activity of total seedling homogenates by ab out 60%. Following centrifugation of homogenates from seedlings of various ages, ca. 80% of the recovered lipolytic activity was located in the fat-fr ee supernatant, with the remainder in the floating fat pad. The crude seed lipase did not show hydrolytic specificity for glycerol esters of lauric ac id (the predominant fatty acid of the seed triglycerol): comparable lipolyt ic activities were seen toward olive oil, trilaurin, tripalmitin, and trist earin. Maximal lipolytic activity occurred at pH 8.5. This activity was sta ble over the pH range 6 to 9, and unstable at > 40 degreesC in a fashion th at suggested the presence of multiple enzymes with different substrate spec ificities. Two lipolytic species, one of which showed some selectivity towa rd lauric acid esters, were partially separated from one another by ion-exc hange chromatography.