Several polylactosamine-modifying glycosyltransferases also use internal GalNAc 1-4GlcNAc units of synthetic saccharides as acceptors

• Published in: Glycobiology (Oxford) 2002-03, Vol.12 (3), p.217-228
• Main Authors: Salo, H., Aitio, O., Ilves, K., Bencomo, E., Toivonen, S., Penttila, L., Niemela, R., Salminen, H., Grabenhorst, E., Renkonen, R., Renkonen, O.
• Format: Article
• Language: English
• ISSN: 0959-6658; 1460-2423
• DOI: 10.1093/glycob/12.3.217

The GalNAc[beta]1-4GlcNAc determinant (LdN) occurs in some human and bovine glycoconjugates and also in lower vertebrates and invertebrates. It has been found in unsubstituted as well as terminally substituted forms at the distal end of conjugated glycans, but it has not been reported previously at truly internal positions of polylactosamine chains. Here, we describe enzyme-assisted conversion of LdN[beta]1-OR oligosaccharides into GlcNAc[beta]1-3GalNAc[beta]1-4GlcNAc[beta]1-OR. The extension reactions, catalyzed by human serum, were modeled after analogous [beta]3-GlcNAc transfer processes that generate GlcNAc[beta]1-3Gal[beta]1-4GlcNAc[beta]1-OR. The newly synthesized GlcNAc[beta]1-3GalNAc linkages were unambiguously identified by nuclear magnetic resonance data, including the appropriate long-range correlations in heteronuclear multiple bond correlation spectra. The novel GlcNAc[beta]1-3'LdN determinant proved to be a functional acceptor for several mammalian glycosyltransferases, suggesting that human polylactosamines may contain internal LdN units in many distinct forms. The GlcNAc[beta]1-3'LdN determinant was unusually resistant toward jackbean [beta]-N-acetylhexosaminidase; the slow degradation should lead to a convenient method for the search of putative internal LdN determinants in natural polylactosamine chains.