Blixt O, Van Die I, Norberg T, van den Eijnden DH High-level expression of the Neisseria meningitidis lgtA gene in Escherichia coli and characterization of the encoded N-acetylglucosaminyltransferase as a useful catalyst in the synthesis of GlcNAcb1→3Gal and GalNAcb1-3Gal linkages Glycobiology9(10) (1999)
1061-1071
NCBI PubMed ID:10521543 Publication DOI:10.1093/glycob/9.10.1061 Journal NLM ID:9104124 Publisher: 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
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.
Methods: 13C NMR, 1H NMR, NMR-2D, SDS-PAGE, enzyme-assisted synthesis, DNA techniques, glycosyltransferase assays, kinetics assays Enzymes that release or process the structure: LgtA Biosynthesis and genetic data: biosynthesis data Synthetic data: enzymatic Comments, role: acceptor (1 mM theoretical acceptor sites), relative enzyme activity with UDP-GlcNAc 2.0%, relative enzyme activity with UDP-GalNAc was not determined
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