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. Author manuscript; available in PMC: 2020 Aug 1.
Published in final edited form as: Curr Opin Cell Biol. 2019 Apr 28;59:58–72. doi: 10.1016/j.ceb.2019.03.012

Figure 1.

Figure 1

Phosphoinositides and their metabolism. Phosphoinositides are phosphorylated derivatives of phosphatidylinositol (PtdIns) and their production is catalyzed by distinct sets of lipid kinases that modify either the C3, C4 or C5 positions of the inositol headgroup. Reciprocally, phosphoinositides are dephosphorylated via the action of a cohort of phosphoinositide phosphatases. Whereas mammalian cells produce seven phosphoinositides [PtdIns 3-phosphate, PtdIns3P; PtdIns 4-phosphate, PtdIns(4)P; PtdIns-5-phosphate, PtdIns5P; PtdIns 3,5-bisphosphate, PtdIns(3,5)P2; PtdIns 4,5-bisphosphate PtdIns(4,5)P2; PtdIns 3,4-bisphosphate, PtdIns(3,4)P2; PtdIns 3,4,5-triphosphate, PtdIns(3,4,5)P3], most organisms produce fewer. For example, baker’s yeast (Saccharomyces cerevisiae) and plants produce the first five, but lack the capacity to produce PtdIns(3,4)P2 or PtdIns(3,4,5)P3. PtdIns(4)P metabolism is highlighted in this figure as this phosphoinositide is the focus of discussion.