LacNAccontaining

LacNAc-containing refers to glycans that include the disaccharide N-acetyllactosamine (Galβ1-4GlcNAc) as a recurring unit. These LacNAc units are common building blocks on N- and O-linked glycans and on certain glycolipids, where they can be found as short chains or as extended poly-N-acetyllactosamine (poly-LacNAc) repeats.

Biosynthesis and structure occur in the Golgi and involve glycosyltransferases of the B4GALT family that add galactose in a beta-1,4 linkage to N-acetylglucosamine, followed by N-acetylglucosaminyltransferases (such as B3GNTs) that extend the chain with GlcNAc residues. Repeated cycles generate poly-LacNAc structures longer than two units. Modifications such as sialylation (sialyl-LacNAc) or fucosylation yield additional motifs and binding epitopes.

Occurrence and function: these motifs are abundant on diverse glycoproteins, including mucins and cell-surface receptors, and on glycolipids. They provide ligands for carbohydrate-binding proteins such as galectins, influencing cell–cell adhesion, signaling, and receptor organization. The length and modification state of LacNAc-containing chains can affect antigenicity and interactions with lectins and microbes.

Clinical significance: changes in LacNAc-containing glycans are observed in development and disease, notably cancer, where extended poly-LacNAc chains or sialyl-LacNAc motifs can alter cell adhesion, migration, and immune recognition. They also participate in host–pathogen interactions by serving as attachment factors for various microbes.

See also: N-acetyllactosamine, poly-N-acetyllactosamine, galectins, sialyl-LacNAc, Lewis antigens.