Nucleotide sugar antiporter transporting UDP-N- acetylglucosamine (UDP-GlcNAc) and UDP-glucose (UDP-Glc) from the cytosol into the lumen of the Golgi in exchange of UMP. By supplying UDP-N-acetylglucosamine, a donor substrate to heparan sulfate synthases, probably takes part in the synthesis of these glycoconjugates. {ECO:0000305|PubMed:15082721, ECO:0000305|PubMed:15607426}. This is the function of SLC35D2 (solute carrier family 35 member D2, ENSG00000130958).