Keratan Sulfate - Keratan Sulfate Structure

Keratan Sulfate Structure

Like other glycosaminoglycans keratan sulfate is a linear polymer that consists of a repeating disaccharide unit. Keratan sulfate occurs as a proteoglycan (PG) in which KS chains are attached to cell-surface or extracellular matrix proteins, termed core proteins. KS core proteins include Lumican, Keratocan, Mimecan, Fibromodulin, PRELP, Osteoadherin and Aggrecan.

The basic repeating disaccharide unit within keratan sulfate is -3Galβ1-4GlcNAcβ1-. This can be sulfated at carbon position 6 (C6) of either or both the Gal or GlcNAc monosaccharides. However, the detailed primary structure of specific KS types are best considered to be composed of three regions:

• A linkage region, at one end of which the KS chain is linked to the core protein.
• A repeat region, composed of the -3Galβ1-4GlcNAcβ1- repeating disaccharide unit and
• A chain capping region, occurring at the opposite end of the KS chain to the protein linkage region.

The monosaccharide mannose is found within the linkage region of keratan sulfate type I (KSI). Disaccharides within the repeating region of KSII may be fucosylated and N-Acetylneuraminic acid caps the end of all keratan sulfate type II (KSII) chains and up to 70% of KSI type chains.