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phosphatidylinositol

(Science: biochemistry) A phosphatidic acid combined with inositol found in biomembranes and a precursor to certain cellular signals. Sometimes referred to as inositide.

It is a 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 (Ins P3: iP3). Both the diacyl glycerol and products act as second messengers.

Synonym: phosphoinositide.