Neu5Ac23Gal13Fuc14GlcNAc

Neu5Ac23Gal13Fuc14GlcNAc denotes a tetrasaccharide motif in which N-acetylneuraminic acid (Neu5Ac) is linked alpha2-3 to galactose (Gal), which is beta1-3 linked to fucose (Fuc) that is alpha1-4 linked to N-acetylglucosamine (GlcNAc). This arrangement corresponds to the sialyl Lewis A (sLea) antigen, a sialylated Lewis-type epitope found on glycoproteins and glycosphingolipids in human tissues.

Biosynthesis of this motif involves the coordinated action of glycosyltransferases. A sialyltransferase of the ST3Gal family adds Neu5Ac to Gal (alpha2-3 linkage), while an alpha1-4 fucosyltransferase, typically FUT3, attaches Fuc to GlcNAc (to form the Lewis A core). The presence of sLea depends on the expression and activity of FUT3 and compatible glycosyltransferases in specific cell types, often at mucin-bearing surfaces.

Biological and clinical significance of sLea include its role as a ligand for selectins, contributing to leukocyte adhesion and trafficking. It is also a well-known tumor-associated carbohydrate antigen. Clinically, the sialyl-Lewis A determinant is the basis of the CA19-9 tumor marker used in monitoring pancreatic, biliary, and colorectal cancers. Expression of sLea can be upregulated in malignant cells, while normal tissues generally exhibit lower levels.

Occurrence and detection of sLea occur on mucins and other glycoproteins on epithelial surfaces and secretions. Detection in serum or tissue samples is used in research and diagnostics, with utility varying by context and alongside other markers.