Phosphatidylinositol and Related Lipids

Phosphatidylinositol is an important lipid, both as a key membrane constituent and as a participant in essential metabolic processes in all plants and animals, both directly and via a number of metabolites. It is an acidic (anionic) phospholipid that in essence consists of a phosphatidic acid backbone, linked via the phosphate group to inositol (hexahydroxycyclohexane). In most organisms, the stereochemical form of the latter is myo-D-inositol (with one axial hydroxyl in position 2 with the remainder equatorial), although other forms (scylloand chiro) have been found on occasion in plants. The 1-stearoyl,2-arachidonoyl molecular species, which is of considerable biological importance in animals, is illustrated.