The bifunctional enzymes heparan sulfate N-deacetylases/N-sulfotransferases 1-4 (NDST1-4) catalyse both the N-deacetylation and the N-sulfation of N-acetylglucosamine (GlcNAc) of heparan (Dixon et al. 1995, Duncan et al. 2006, Aikawa & Esko 1999, Aikawa et al. 2001). Once GlcNAc is deacetylated to glucosamine, the NDST enzymes can sulfate it on position 2 (N).