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. Ethanolamine phosphate on the alpha-1,4-linked mannose is essential for further mannosylation by GPI10 and is necessary for an efficient recognition of GPI lipids and GPI proteins by the GPI transamidase, for the efficient transport of GPI anchored proteins from endoplasmic reticulum to Golgi and for the physiological incorporation of ceramides into GPI anchors by lipid remodeling. Also involved in non-mitochondrial ATP movements across membrane and participates in Golgi and endoplasmic reticulum function, Also required for the incorporation of BGL2 into the cell wall. Glycolipid biosynthesis; glycosylphosphatidylinositol-anchor biosynthesis. N-glycosylated. Target of the inhibitor of GPI biosynthesis YW3548/BE49385A. Belongs to the PIGG/PIGN/PIGO family. PIGN subfamily.