B4GALNT3 transfers N-acetylgalactosamine (GalNAc) onto glucosyl residues to form N,N-prime-diacetyllactosediamine (LacdiNAc, or LDN), a unique terminal structure of cell surface N-glycans (Ikehara et al., 2006 [PubMed 16728562]).[supplied by OMIM, Aug 2008].