With regard to HSGAGs, a multimeric enzyme encoded by EXT1 and EXT2 of the EXT family of genes, transfers both GlcNAc and GlcA for HSGAG chain elongation. While elongating, the HSGAG is dynamically modified, first by N-deacetylase, N-sulfotransferase (NDST1), which is a bifunctional enzyme that cleaves the N-acetyl group from GlcNAc and subsequently sulfates the N-position. Next, C-5 uronyl epimerase coverts d-GlcA to l-IdoA followed by 2-"O" sulfation of the uronic acid sugar by 2-"O" sulfotransferase (Heparan sulfate 2-O-sulfotransferase). Finally, the 6-"O" and 3-"O" positions of GlcNAc moities are sulfated by 6-"O" (Heparan sulfate 6-O-sulfotransferase) and 3-O (3-OST) sulfotransferases.