 Phosphatidylinositol phosphate kinases

Phosphatidylinositol phosphate kinases (PIPK) are kinases that phosphorylate the phosphoinositides PtdIns"P" and PtdIns"P"2 that are derivatives of phosphatidylinositol (PtdIns).It has been found that PtdIns is only phosphorylated on three (3,4,5) of its five hydroxyl groups, possibly because D-2 and D-6 hydroxyl groups cannot be phosphorylated because of steric hindrance.