Phosphatidylinositol ( English Phosphatidylinositol, PtdIns, PI ) is a minor phospholipid of the inner layer of eukaryotic cell membranes, an important component of intracellular signaling pathways.
Composition
Phosphatidylinositol consists of a glycerol base, to which in positions 1 and 2 two fatty acid chains are attached, and in position 3 - a phosphate group and inositol . Inositol, a six-basic cyclic alcohol , is found in the phosphatidyl-inositol molecule in the stereoisomeric form of myo- inositol.
Role in biology
Phosphatidylinositol is a substrate for a wide variety of signaling kinase molecules that can attach a phosphate group to inositol. Three of the five free hydroxyl groups of the inositol ring at positions 3, 4, and 5 can be phosphorylated by the action of such kinases . Obviously, positions 2 and 6 are inaccessible to these enzymes due to steric hindrance . A total of 7 variants of mono-, di- or triphosphate phosphatidylinositol derivatives are possible. All 7 were found in animal cells, while all were found in plants with the exception of phosphatidylinositol-3,4,5-triphosphate .
See also
- Phosphatidylinositol-3-phosphate