Biosynthesis of sulfated glycoprotein-N-glycans present in recombinant human tissue plasminogen activator

Abstract Recombinant human tissue plasminogen activator expressed in murine epithelial cells carries, in part, sulfated N -glycans, which are characterized by the presence of a NeuAcα3[SO 4 -6]Gal unit. In order to study the biosynthesis of this novel structural element, corresponding sulfated asialooligosaccharide alditols were resialylated in vitro using a crude sialyltransferase preparation from murine liver which was shown to contain Gals1,3(4)GlcNAc α2,3-sialyltransferase activity. Products were analyzed for transfer of sialic acid residues by anion-exchange HPLC. The results demonstrated that resialylation of SO 4 -6Gal-residues did not occur. Therefore, it may be concluded that transfer of the sulfate group is the final step in the biosynthesis of this structural epitope.