Heparan sulfate (HS) is a linear polysaccharide composed of 50–200 glucosamine and
uronic acid (glucuronic acid or iduronic acid) disaccharide repeats with epimerization and
various sulfation modifications. HS is covalently attached to core proteins to form HS-
proteoglycans. Most of the functions of HS-proteoglycans are mediated by their HS moieties.
The biosynthesis of HS is initiated by chain polymerization and is followed by stepwise
modification reactions, including sulfation and epimerization. These modifications generate …