Figure 1. EDI3 cleaves glycerophosphocholine (GPC) to choline and glycerol-3-phosphate (G3P). (A) Activity of the purified EDI3 protein which metabolizes GPC to form G3P. Additional generation of choline has been demonstrated by an enzyme-coupled spectrophotometric assay. (B) Knockdown of EDI3 in MCF-7 cells increases intracellular concentrations of the substrate GPC and decreases phosphocholine (PC), which is formed from the product, choline (from Stewart et al., 2012).¹