EC - UDP-N-acetylglucosamine 4,6-dehydratase (inverting)

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IntEnz Enzyme Nomenclature


Accepted name:
UDP-N-acetylglucosamine 4,6-dehydratase (inverting)
Other names:
UDP-N-acetylglucosamine hydro-lyase (inverting; UDP-2-acetamido-2,6-dideoxy-β-L-arabino-hex-4-ulose-forming)
UDP-N-acetylglucosamine 5-inverting 4,6-dehydratase
Systematic name:
UDP-N-acetyl-α-D-glucosamine hydro-lyase (inverting; UDP-2-acetamido-2,6-dideoxy-β-L-arabino-hex-4-ulose-forming)




Contains NADP+ as a cofactor. This is the first enzyme in the biosynthetic pathway of pseudaminic acid [3], a sialic-acid-like sugar that is unique to bacteria and is used by Helicobacter pylori to modify its flagellin. This enzyme plays a critical role in H. pylori's pathogenesis, being involved in the synthesis of both functional flagella and lipopolysaccharides [1,2]. It is completely inhibited by UDP-α-D-galactose. The reaction results in the chirality of the C-5 atom being inverted. It is thought that Lys-133 acts sequentially as a catalytic acid, protonating the C-6 hydroxy group and as a catalytic base, abstracting the C-5 proton, resulting in the elimination of water. This enzyme belongs to the short-chain dehydrogenase/reductase family of enzymes.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB


  1. Ishiyama, N., Creuzenet, C., Miller, W.L., Demendi, M., Anderson, E.M., Harauz, G., Lam, J.S. and Berghuis, A.M.
    Structural studies of FlaA1 from Helicobacter pylori reveal the mechanism for inverting 4,6-dehydratase activity.
    J. Biol. Chem. 281 : 24489-24495 (2006). [PMID: 16651261]
  2. Schirm, M., Soo, E.C., Aubry, A.J., Austin, J., Thibault, P. and Logan, S.M.
    Structural, genetic and functional characterization of the flagellin glycosylation process in Helicobacter pylori.
    Mol. Microbiol. 48 : 1579-1592 (2003). [PMID: 12791140]
  3. Schoenhofen, I.C., McNally, D.J., Brisson, J.R. and Logan, S.M.
    Elucidation of the CMP-pseudaminic acid pathway in Helicobacter pylori: synthesis from UDP-N-acetylglucosamine by a single enzymatic reaction.
    Glycobiology 16 : 8C-14C (2006). [PMID: 16751642]

[EC created 2009]