D-myo-inositol (1,4,5)-trisphosphate biosynthesis is a pathway that occurs in the cytosol by which myo-inositol becomes D-myo-inositol (1,4,5)-trisphosphate (IP3), a secondary messenger molecule used in signal transduction and lipid signaling in biological cells . This pathway consists of a few cell membrane-associated enzymes (coloured dark green in the image): phosphatidylinositol 4-phosphate 5-kinase and phosphoinositide phospholipase C. First, phosphatidylinositol synthase uses a a CDP-diacylglycerol to catalyze a reaction whereby myo-inositol is converted into an an L-1-phosphatidyl-inositol. It requires magnesium or manganese ions as cofactors. Second, phosphatidylinositol 4-kinase uses ATP to catalyze the conversion of an L-1-phosphatidyl-inositol to a 1-phosphatidyl-1D-myo-inositol 4-phosphate. Third, phosphatidylinositol 4-phosphate 5-kinase uses ATP to catalyze the conversion of a 1-phosphatidyl-1D-myo-inositol 4-phosphate to a 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate. Alternatively, 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate is predicted to be synthesized by a still undiscovered phosphatidylinositol-5-phosphate 4-kinase from ATP and a 1-phosphatidyl-1D-myo-inositol 5-phosphate. Finally, phosphoinositide phospholipase C uses water to catalyze the conversion of a 1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate to D-myo-inositol (1,4,5)-trisphosphate, producing 1,2-diacyl-sn-glycerol and a proton as byproducts. Phosphoinositide phospholipase C requires calcium as a cofactor.

D-myo-Inositol (1,4,5)-Trisphosphate Biosynthesis References