• The GalNAcT-I activity catalyzes GalNAc transfer toward GlcA in the linkage tetrasaccharide (GlcAβ1-3Galβ1-3Galβ1-4Xylβ1-). This is strongly mediated by CSGalNAcT1 (ChGn1) but can also be performed by CSGalNAcT-II (ChGn2).
• GalNAcT-II catalyzes elongation activity to create repeating disaccharide unit (GlcAβ1-3GalNAcβ1-4)n in the CS chain. This is more readily performed by CSGalNAcT2. Mice lacking CSGalNAcT1 exhibit dwarf phenotype with less cartilage development
• Overall, CSGalNAcT1 and CSGalNAcT2 mediate both initiation and elongation of CS via GalNAcT activity
• CHSY1 (Chondroitin synthase-1/chondroitin sulfate synthase-1 (CSS1)) and CHSY3 (chondroitin synthase-3/chondroitin sulfate synthase-3 (CSS3)) exhibit dual glycosyltransferase activities of β1,3 GlcA-T and β1,4 GalNAc-T for CS initiation and elongation
• CHPF (chondroitin sulfate synthase-2 (CSS2)) also exhibits dual glycosyltransferase activities of β1,3 GlcA-T and β1,4 GalNAc-T for CS initiation and elongation. Its activity is similar to that of CSS1 and CSS3.
• CHPF2 (chondroitin polymerizing factor 2/chondroitin sulfate glucuronyltransferase (CSGlcA-T)) transfers glucuronic acid (GlcUA) from UDP-GlcUA to N-acetylgalactosamine in the elongating chondroitin polymer. It does not have GalNAcT activity.
• CS is also present broadly in the tissues and abundantly in the cartilage and brain. Aggrecan contains abundant CS in cartilage.