ID 5.1.3.17 DE heparosan-N-sulfate-glucuronate 5-epimerase. CA [heparosan-N-sulfate](n) = [heparan-N-sulfate](n). CC -!- The enzyme acts on D-glucosyluronate residues in N-sulfated heparosan CC polymers, converting them to L-iduronate, thus modifying the polymer CC to heparan-N-sulfate. CC -!- The enzyme requires that at least the N-acetylglucosamine residue CC linked to C-4 of the substrate has been deacetylated and N-sulfated, CC and activity is highest with fully N-sulfated substrate. CC -!- It does not act on glucuronate residues that are O-sulfated or are CC adjacent to N-acetylglucosamine residues that are O-sulfated at the 6 CC position. CC -!- Thus the epimerization from D-glucuronate to L-iduronate occurs after CC N-sulfation of glucosamine residues but before O-sulfation. CC -!- Not identical with EC 5.1.3.19 or with EC 5.1.3.36. DR F1QR43, GLCEB_DANRE; O18756, GLCE_BOVIN ; P46555, GLCE_CAEEL ; DR O94923, GLCE_HUMAN ; Q9EPS3, GLCE_MOUSE ; //