Ethanolamine phosphate transferase involved in glycosylphosphatidylinositol-anchor biosynthesis. Transfers ethanolamine phosphate to the first alpha-1,4-linked mannose of the glycosylphosphatidylinositol precursor of GPI-anchor. May act as suppressor of replication stress and chromosome missegregation. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. Target of the inhibitor of GPI biosynthesis YW3548/BE49385A. Belongs to the PIGG/PIGN/PIGO family. PIGN subfamily.