Figure 3.

Signalling lipids are interconverted by a variety of enzymes. Phosphoinositides are phosphoglycerolipids carrying an inositol headgroup. Phosphorylation of different hydroxyl groups of the inositol in phosphatidylinositol (PI) gives rise to different mono- and diphosphorylated phosphoinositides. Phospholipase C-activity cleaves the bond to the sn3-hydroxyl group of the glycerol backbone, yielding diacylglycerol (DAG) in the process, which can be phosphorylated to phosphatidic acid (PA). Used abbreviations: DAG—diacylglycerol, IP₃—inositol 1,4,5-trisphosphate, IP₆—inositolhexakisphosphate, PA—phosphatidic acid, PI—phosphatidylinositol, PI3P—phosphatidylinositol 3-phosphate, PI4P—phosphatidylinositol 4-phosphate, PI(3,5)P₂—phosphatidylinositol 3,5-bisphosphate, PI(4,5)P₂—phosphatidylinositol 4,5-bisphosphate, PI-PLC—phosphoinositide phospholipase C, PLD—phospholipase D.