Cell-surface glycoconjugates bearing terminal β-galactose (Terminal β-gal glycoconjugates)

Cell-surface glycoconjugates bearing terminal β-galactose are complex carbohydrate structures, including glycoproteins and glycolipids, where a β-galactose residue occupies the terminal, non-reducing position. In physiological conditions, these residues are often masked by terminal sialic acid; their exposure, often termed desialylation, acts as a biological clock for the clearance of aged cells and glycoproteins from circulation via the asialoglycoprotein receptor (ASGPR) in the liver (D'Souza & Devarajan, 2015). These glycoconjugates are significant in oncology, as truncated or altered glycosylation patterns often lead to the overexposure of terminal galactose, such as the Thomsen-Friedenreich (TF) antigen, which promotes tumor cell adhesion and metastasis (Springer, 1984). They serve as primary binding sites for various potent toxins like ricin and abrin, which utilize the galactose-binding B-chain to enter host cells (Lord et al., 1994). Furthermore, the high affinity of hepatic receptors for these structures has been exploited in pharmacology for the targeted delivery of siRNA and other therapeutics using galactose or N-acetylgalactosamine (GalNAc) conjugation (Nair et al., 2014).

Other names

Terminal beta-galactose residuesGalactose-terminated glycansβ-Gal-terminated glycoconjugatesDesialylated glycoconjugatesAsialoglycansTF antigen (related)

Binding to terminal galactose residues facilitates cellular entry of toxins or targeted delivery of therapeutic payloads via receptor-mediated endocytosis (Lord et al., 1994; Nair et al., 2014).