Keratan sulfate/keratin metabolism

Keratan sulfate (KS) (a glycosaminoglycan, GAG) is a linear polysaccharide that consists of the repeating disaccharide unit GlcNAc-Gal (N-acetylglucosamine-galactose). KS can perform a structural function and is found in bone, cartilage and the cornea. In joints, it also acts as a shock absorber due to its highly hydrated nature. There are several classes of KS, KSI, II and III. KSI is N-linked to asparagine (Asn) residues in the core protein and is predominantly found in the cornea. KSII is O-linked to serine (Ser) or Thr (threonine) residues in the core protein and is found predominantly in cartilage linked to the protein aggrecan, forming the most abundant proteoglycan in cartilage. A third class of KS, KSIII, are proteoglycans in the brain. KSIII chains are linked to Ser/Thr residues in the core protein via mannose.

Summary from Reactome (R-HSA-1638074), read 2026-09-23.