Keratan Sulfate, a “Unique” Sulfo-Sugar: Structures, Functions, and Synthesis

Keratan sulfate is a sulfated polysaccharide classified as a glycosaminoglycan, which has the structurally unique characteristics of diversity in the linker oligosaccharides connecting to the core protein, the existence of both an intrachain fucose branch and a "capping" monosaccharide at the nonreducing end, and diversity of the sulfation patterns. The function(s) of this newest glycosaminoglycan, keratan sulfate, remain mostly unclear. In this minireview, we describe the structures and known functions of keratan sulfate as well as cutting-edge methods to enable the synthesis of keratan sulfate with complex structures.