title: Several polylactosamine-modifying glycosyltransferases also use internal GalNAcbeta1-4GlcNAc units of synthetic saccharides as acceptors.
abstract: The GalNAcbeta1-4GlcNAc 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 LdNbeta1-OR oligosaccharides into GlcNAcbeta1-3GalNAcbeta1-4GlcNAcbeta1-OR. The extension reactions, catalyzed by human serum, were modeled after analogous beta3-GlcNAc transfer processes that generate GlcNAcbeta1-3Galbeta1-4GlcNAcbeta1-OR. The newly synthesized GlcNAcbeta1-3GalNAc linkages were unambiguously identified by nuclear magnetic resonance data, including the appropriate long-range correlations in heteronuclear multiple bond correlation spectra. The novel GlcNAcbeta1-3'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 GlcNAcbeta1-3'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.
authors.affiliation: Institute of Biotechnology, Laboratory of Glycobiology, FIN-00014 University of Helsinki, Finland.
authors.forename: Hanna
authors.initials: H
authors.lastname: Salo
authors.forename: Olli
authors.initials: O
authors.lastname: Aitio
authors.forename: Kristiina
authors.initials: K
authors.lastname: Ilves
authors.forename: Eija
authors.initials: E
authors.lastname: Bencomo
authors.forename: Suvi
authors.initials: S
authors.lastname: Toivonen
authors.forename: Leena
authors.initials: L
authors.lastname: Penttilä
authors.forename: Ritva
authors.initials: R
authors.lastname: Niemelä
authors.forename: Heidi
authors.initials: H
authors.lastname: Salminen
authors.forename: Eckart
authors.initials: E
authors.lastname: Grabenhorst
authors.forename: Risto
authors.initials: R
authors.lastname: Renkonen
authors.forename: Ossi
authors.initials: O
authors.lastname: Renkonen
mesh_terms: D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D005688:Galactosamine / Q000378:metabolism*; D016695:Glycosyltransferases / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D004187:Disaccharides; D009844:Oligosaccharides; D011134:Polysaccharides; D011994:Recombinant Proteins; D005688:Galactosamine; D016695:Glycosyltransferases