Uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) transporter in the Golgi apparatus. May supply UDP-GlcNAc as substrate for Golgi-resident glycosyltransferases that generate branching of diantennary oligosaccharides. Interacts with SLC35A2; the interaction is reduced in the presence of SLC35A4 (PubMed:23089177, PubMed:28167211). Found in a complex with SLC35A2 and SLC35A4 (PubMed:28167211). The disease is caused by variants affecting the gene represented in this entry. In Golgi vesicles isolated from patient fibroblasts the transport of the respective nucleotide sugar is significantly reduced causing a massive decrease in the content of cell surface expressed highly branched N-glycans and a concomitant sharp increase of lower branched glycoforms. Belongs to the nucleotide-sugar transporter family. SLC35A subfamily.