Nucleotide sugars, which are synthesized in the cytosol or the nucleus, are high-energy donor substrates for glycosyltransferases located in the lumen of the endoplasmic reticulum and Golgi apparatus. Translocation of nucleotide sugars from the cytosol into the lumen compartment is mediated by specific nucleotide sugar transporters, such as SLC35D2 (Suda et al., 2004 [PubMed 15082721]).[supplied by OMIM, Mar 2008].