Sialyltransferases are enzymes that catalyse the transfer of sialic acid from its activated sugar nucleotide form, cytidine 5'-monophosphate sialic acid (CMP-sialic acid or CMP-Sia), to the terminal positions of glycans on glycoproteins and glycolipids.

The second and third domains in certain sialyltransferases resemble the Rossmann nucleotide-binding domain. Together, these two domains form a structure found in the glycosyltransferase B (GT-B) superfamily, and hence they are named N-terminal GT-B and C-terminal GT-B domains. A deep nucleotide-binding cleft is formed between the two domains that can accommodate substrate molecules of varied sizes and diverse structures and exhibits a large conformational change of the enzyme upon binding to CMP.

This superfamily entry is representative for the N-terminal GT-B glycosyltransferase B domain.

DOI:10.1016/j.febslet.2014.11.003,DOI:10.1021/bi0524013