Chondroitin sulfate (CS) biosynthesis is initiated by the addition of xylose to serine residues in a core protein, followed by the sequential addition of two Gal residues and a GlcA residue to form the tetrasaccharide linkage structure GlcAβ1-3Galβ1-3Galβ1-4Xylβ1- O -Ser. Chondroitin...