Oleosomes (Spherosomes) from Daucus carota suspension culture cells.

Isolated oleosomes from Daucus carota L. cells are lipid droplets consisting mainly of triacylglycerols (>97%) and very little protein (1-2%). The boundary between the lipid phase and the cytosol, which is visible on electron micrographs, is not built up by a true phospholipid-containing unit or half unit membrane. Enzymatic activities of lipid metabolism were not found to be associated with oleosomes with the exception of very low (contaminating) acyl-CoA:1,2-diacylglycerol acyltransferase (EC 2.3.1.20) and relatively high acyl-CoA hydrolase (EC 3.1.2.2) activities. The triacylglycerols exhibited a half life time of about 70 h, which is below the generation time of the cells (80-90 h). The fatty acid pattern of triacylglycerols was very similar to that of polar cellular membrane lipids.