- phosphatidyl inositol
Very important minor phospholipid in eukaryotes, involved in signal transduction processes. Contains myo-inositol linked through the 1-hydroxyl group to phosphatidic acid. The 4-phosphate (PIP) and 4,5 bisphosphate derivatives (PIP2) are formed and broken down in membranes by the action of specific kinases and phosphatases (futile cycles). Signal-sensitive phospholipase C enzymes remove the inositol moiety, in particular from 1,4,5 trisphosphate (PIP2) as inositol 1,4,5-triphosphate (InsP3: IP3). Both the diacyl glycerol and inositol phosphate products act as second messengers.
Dictionary of molecular biology. 2004.