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. Author manuscript; available in PMC: 2022 May 31.
Published in final edited form as: FEBS J. 2019 Nov 21;287(2):222–238. doi: 10.1111/febs.15127

Figure 1. Phosphoinositide cycle.

Figure 1.

Phosphoinositides are a small group of phospholipids generated by the phosphorylation of the third, fourth and fifth positions of the inositol headgroup of phosphatidylinositol. The seven resulting phosphoinositides are cycled and regulated by a complex network of kinases and phosphatases that add or remove phosphate groups at specific positions. The precision of these enzymes is what keeps the phosphoinositide pools within a cell in perfect balance. The kinases (left) and phosphatases (right) are numbered, and the indicated number corresponds to the enzymes that allow the cycling between each of the phosphoinositide species starting with phosphatidylinositol (PI) at the center. Dashed grey arrows indicate enzymes that have not yet been characterized in vivo (Unknown).