Essential protein. Glycosyltransferase that mediates the glycosylation of glycosylinositol phosphorylceramides (GIPCs), the major sphingolipids in the plasma membrane; acts as a HexN(Ac)-specific GIPC sugar transferase. Responsible for the glycosylation of a subgroup of GIPCs found in seeds and pollen that contain GlcNAc and GlcN (GlcN(Ac)). Maybe involved in the maintenance of cell-cell adhesion