SYNTHESIS OF NEOGLYCOCONJUGATES CONTAINING DEAMINATED NEURAMINIC ACID(KDN) USING RAT-LIVER ALPHA-2,6-SIALYLTRANSFERASE

2-Keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) was introduced i nto asialotransferrin and N-acetyllactosamine (LacNAc) from CMP-KDN by using rat liver Gal beta 1-->4GlcNAc alpha 2,6-sialyltransferase to f orm KDN-transferrin and KDN-LacNAc. These structures contain terminal KDN alpha 2-->6Gal-residues, a glycotope that has not yet been describ ed in natural glycoconjugates. KDN was transferred to all four Gal res idues in asialotransferrin by this enzyme. The incorporation efficienc y of KDN from CMP-KDN into asialotransferrin was about half that of Ne u5Ac from CMP-Neu5Ac, based on the V-max/K-m values for these donor su bstrates, 0.0527 min(-1) and 0.119 min(-1), respectively. The KDN alph a 2-->6Gal linkage was resistant to exosialidase treatment, in contras t to the sensitivity of the Neu5Ac alpha 2-->6Gal linkage. Interesting ly, Sambucus sieboldiana agglutinin (SSA) was shown to prefer KDN-tran sferrin to the corresponding Neu5Ac-transferrin, as estimated by slot- blot analysis. The use of an alpha 2,6-sialyltransferase to synthesize neoglycoproteins containing KDN has not been previously reported. The ir facile synthesis using CMP-KDN and sialyltransferases with differen t specificities offers new possibilities to study the function of neo- KDN-glycoconjugates, and to explore their use in glycotechnology.