Synthesis of neoglycoconjugates containing deaminated neuraminic acid (KDN) using rat liver alpha2,6-sialyltransferase

2-Keto-3-deoxy-D- glycero -D- galacto -nononic acid (KDN) was introducedinto asialotransferrin and N -acetyllactosamine (LacNAc) from CMP-KDN byusing rat liver Galbeta1-->4GlcNAc alpha2, 6- sialyltransferase to formKDN-transferrin and KDN-LacNAc. These structures contain terminalKDNalpha2-->6Gal-residues, a glycotope that has not yet been describedin natural glycoconjugates. KDN was transferred to all four Gal residues inasialotransferrin by this enzyme. The incorporation efficiency of KDN fromCMP-KDN into asialotransferrin was about half that of Neu5Ac fromCMP-Neu5Ac, based on the V max/ K m values for these donor substrates,0.0527 min-1and 0.119 min-1, respectively. The KDNalpha2-->6Gal linkagewas resistant to exosialidase treatment, in contrast to the sensitivity ofthe Neu5Acalpha2-->6Gal linkage. Interestingly, Sambucus sieboldianaagglutinin (SSA) was shown to prefer KDN-transferrin to the correspondingNeu5Ac-transferrin, as estimated by slot-blot analysis. The use of analpha2,6-sialyltransferase to synthesize neoglycoproteins containing KDNhas not been previously reported. Their facile synthesis using CMP-KDN andsialyltransferases with different specificities offers new possibilities tostudy the function of neo-KDN- glycoconjugates, and to explore their use inglycotechnology.