Synthesis of sialyl TN Glycopeptides -: Enzymatic sialylation by α2,6-sialyltransferase from Photobacterium damsela

The alpha 2,6-sialyltransferase from Photobacterium damsela was applied for the enzymatic sialylation of the T-N glycopeptide (APGSTA) with GalNAc alpha-linked to either the serine or threonine residue in the sequence. The enzyme preparation and reaction conditions were optimized prior to the application. In contrast to the mammalian sialyltransferases which recognize the moiety of GalNAc alpha(1,1)Thr only, this bacterial enzyme can accept GalNAc alpha(1,1)Thr as well as GalNAc alpha(1,1)Ser. Our study also introduced a 4-dimethylaminoazobenzene-4'-sulfonyl (dabsyl) chromophore to the N-terminus of the peptide backbone, which is suitable for glycoconjugate substrates without affecting the binding affinity.