A sialyl T-antigen-linked tetrapeptide was prepared by the combined method of chemical synthesis and enzymatic synthesis. The GalNAc-linked peptide was first obtained by using a commercial peptide synthesizer, and then a galactose residue was attached with β-(1→3)-linkage by transglycosylating with a recombinant β-galactosidase from Bacillus circulans. The sialic acid residue was then combined by α-(2→3)-linkage with sialytransferase from rat liver.
