Based on limited published evidence, POFUT3 is a protein O-fucosyltransferase that catalyzes O-fucosylation of serine or threonine residues in elastin microfibril interface (EMI) domains of target proteins including MMRN1, MMRN2, and EMID1 1. It attaches fucose through O-glycosidic linkages in the endoplasmic reticulum and may facilitate protein folding and secretion of EMI domain-containing proteins 1. POFUT3 may also exhibit alpha-(1,3)-fucosyltransferase activity toward N-glycans in vitro, though in vivo relevance remains unclear 2. By similarity, it may contribute to Lewis X-carrying N-glycan biosynthesis during neural stem cell development 3.