We have expressed the Neisseria meningitidis lgtA gene at a high level in Escherichia coli. The encoded β-N-acetylglucosaminyltransferase, referred to as LgtA, which in the bacterium is involved in the synthesis of the lacto-N-neo-tetraose structural element of the bacterial lipooligosaccharide, was obtained in an enzymatically highly active form. This glycosyltransferase appeared to be unusual in that it displays a broad acceptor specificity toward both α- and β-galactosides, whether structurally related to N- or O-protein-, or lipid-linked oligosaccharides. Product analysis by one- and two-dimensional 400 MHz 1H- and 13C NMR spectroscopy reveals that LgtA catalyzes the introduction of GlcNAc from UDP-GlcNAc in a β1→3-linkage to accepting Gal residues. The enzyme can thus be characterized as a UDP-GlcNAc:Gal α/β-R β 3-N-acetylglucosaminyltransferase. Although lactose is a highly preferred acceptor substrate the recombinant enzyme also acts efficiently on monomeric and dimeric N-acetyllactosamine revealing its potential value in the synthesis of polylactosaminoglycan structures in enzyme assisted procedures. Furthermore, LgtA shows a high donor promiscuity toward UDP-GalNAc, but not toward other UDP-sugars, and can catalyze the introduction of GalNAc in β1→3-linkage to α- or β-Gal in the acceptor structures at moderate rates. LgtA therefore shows promise to be a useful catalyst in the preparative synthesis of both GlcNAc β1→3 Gal and GalNAc β1→3 Gal linkages.
oligosaccharide, enzyme-assisted-synthesis, recombinant glycosyltransferase, glycosidic linkage, polylactosaminoglycan, recombinant glycosyltrasferase
NCBI PubMed ID: 10521543Publication DOI: 10.1093/glycob/9.10.1061Journal NLM ID: 9104124Publisher: IRL Press at Oxford University Press
Institutions: Department of Chemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden, Department of Medical Chemistry, Vrije Universiteit, Van der Boechorstraat 7, 1081 BT Amsterdam, The Netherlands
Methods: 13C NMR, 1H NMR, NMR-2D, SDS-PAGE, enzyme-assisted synthesis, DNA techniques, glycosyltransferase assays, kinetics assays
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