Degradation of hyaluronan and heparan sulfate (HS). (Left) Hyaluronidase (an endoglycosidase) cleaves large chains into smaller fragments, each of which is then sequentially degraded from the nonreducing end. (Right) Degradation of HS. An endo-β-glucuronidase first cleaves large chains into smaller fragments, and each monosaccharide is then removed from the nonreducing end as described in the text. N- and O-sulfate groups must first be removed before exoglycosidases can act. An unusual feature of HS degradation is that this process also involves a synthetic step. After removal of the N-sulfate residue on GlcNSO₄, the nonacetylated glucosamine must first be N-acetylated using acetyl-CoA before α-N-acetylglucosaminidase can cleave this residue.