The Role of the Sda Carbohydrate Antigen and That of Its Cognate Glycosyltransferase B4GALNT2 in Health and Disease

The carbohydrate antigen Sda is expressed on the cells and secretions of the vast majority of Caucasians. The epitope is formed by a terminal GalNAc residue β4-linked to an α3-sialylated galactose. Different carbohydrate chains N- or O-linked to glycoproteins can be terminated by this epitope. The final step of Sda biosynthesis is catalyzed by the GalNAc transferase B4GALNT2. In this review, we discuss the multifaceted aspects of B4GALNT2/Sda in fertility and pregnancy, susceptibility to infectious diseases, cancer, chronic kidney diseases, and Duchenne muscular dystrophy. We show how multiple synthetic biology approaches have been adopted to investigate its role.