Function
Catalyzes the biosynthesis of phosphatidylinositol (PtdIns) as well as PtdIns:inositol exchange reaction (PubMed:17151285, PubMed:24828534, PubMed:24603715). May thus act to reduce an excessive cellular PtdIns content (By similarity). The exchange activity is due to the reverse reaction of PtdIns synthase and is dependent on CMP, which is tightly bound to the enzyme (By similarity). Required for the regeneration of the signaling molecule phosphatidylinositol 4,5-bisphosphate (PtdInsP2) from phosphatidic acid (PA) and maintenance of its steady supply during signaling, thus playing an essential role during phospholipase C-mediated transduction (PubMed:17151285). This function is essential in photoreceptors for light-activated recycling of PtdInsP2 during phototransduction (PubMed:17151285). As a key enzyme of the phosphoinositide pathway, indirectly involved in the polarized secretion of basal membrane (BM) proteins in follicle epithelial (FE) cells through promoting PtdInsP2 synthesis in the apical and lateral plasma membranes of FE cells (PubMed:24828534). PtdInsP2 controls the localization of Crag and perhaps the localization and expression of strat, both of which are essential for restricting the secretion of BM proteins to the basal surface (PubMed:24828534, PubMed:28228250).