disialylation

Disialylation is the presence or enzymatic formation of two sialic acid residues on a glycan, glycoprotein, or glycolipid. It is a specific form of sialylation, distinguishing molecules that carry two terminal sialic acids from those with one (monosialylation) or none (asialylation). In glycoconjugates, disialylation most often refers to disialylated gangliosides, such as GD3, which contain two sialic acid residues linked to underlying galactose units and ceramide backbones.

Biological production is catalyzed by sialyltransferases in the Golgi apparatus. Different enzymes add sialic acid residues in different linkages (for example alpha2,3- or alpha2,6-linkages), and sequential action can yield disialylated motifs on the same chain or on branching sites. Sialidases (neuraminidases) can remove sialic acids, thereby converting disialylated species to monosialylated or asialylated forms, or vice versa by remodeling.

Disialylation influences charge, hydrophilicity, and recognition by lectins and receptors. Terminal sialic acids mask underlying sugars from hepatic clearance receptors, affect cell–cell interactions, and modulate immune recognition via Siglecs. In development and disease, abnormal disialylation patterns have been observed; certain disialylated gangliosides, including GD3, are enriched in neural tissues and are associated with processes such as differentiation, apoptosis, and tumor progression in various cancers.

Analytical detection and characterization rely on mass spectrometry and glycan sequencing, often after chromatographic separation or labeling. Immunochemical methods and lectin-based assays can detect specific disialylated epitopes, whereas antibodies against GD3 and related gangliosides provide targeted tools for study.

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