ABSTRACT
N-acetyl-lactosamine (LN) and N-acetyl-polylactosamine (PLN) are glycans that are components of lipids, O-and N-linked glycoproteins and proteoglycans and are expressed in most if not all cells and tissues in mammals. LN can be expressed as the terminal structure of an oligosaccharide chain, but is often further modifi ed by the addition of fucose, sialic acid and sulfate. Extended LN chains are produced by the repeated alternating addition of β1,4Galactose (β1,4Gal) and β1,3 N-Acetylglucosamine (β1,3GlcNAc) to generate PLN glycans. Although they have been extensively studied for many years, their structures and functions remain unknown for the most part. On red blood cells PLNs serve as scaffolds for many carbohydrate antigens such as ABO, LeX, LeY and sLeX blood groups. LNs and PLNs are of considerable interest because of their ability to interact with a large family of endogenous lectins, the galectins. A great deal of what we know about lactosamine function comes from studies of galectin-1, which preferentially binds to lactosamine on N-and O-glycans. Thus, LN and PLN can affect biological systems in two ways: by directly modulating the properties of the proteins to which they are attached; and by interacting with galectins and other glycan binding proteins.
