A novel strategy for quantification of α2,3- and α2,6-linked sialic acids in sialylated glycoproteins

Sialic acid, a monosaccharide containing nine carbon atoms, is widely distributed in eukaryotic cells. The bound Sialic Acids are mainly present at the glycan ends of glycoconjugates via α2-3 or α2-6 glycosidic bonds, and alterations in their expression levels and linkage types are associated with the progress of many diseases and Tumors. The present study provides a new strategy for quantification of α2,3- and α2,6-linked Sialic Acids in sialylated glycoproteins. In fact, quantification of α2,3-linked Sialic Acids were based on the difference of the bound Sialic Acids in the sample before and after treatment with α2-3 neuraminidase, whereas the α2,6-linked Sialic Acids were equal to the bound Sialic Acids in the α2-3 neuraminidase-treated sample. Subsequently, α2,3/6-linked Sialic Acids in salivary glycoproteins from healthy volunteers and diabetic patients were quantified in accordance with this method. This work provides an accurate method for the quantification of α2,3- and α2,6-linked Sialic Acids in the sialoglycoproteins, which is more instructive for understanding the biological roles of α2,3/6-linked sialic acid in sialoglycoproteins.