Structure of oxalacetate acetylhydrolase, a virulence factor of the chestnut blight fungus

J Biol Chem. 2010 Aug 20;285(34):26685-96. doi: 10.1074/jbc.M110.117804. Epub 2010 Jun 17.


Oxalacetate acetylhydrolase (OAH), a member of the phosphoenolpyruvate mutase/isocitrate lyase superfamily, catalyzes the hydrolysis of oxalacetate to oxalic acid and acetate. This study shows that knock-out of the oah gene in Cryphonectria parasitica, the chestnut blight fungus, reduces the ability of the fungus to form cankers on chestnut trees, suggesting that OAH plays a key role in virulence. OAH was produced in Escherichia coli and purified, and its catalytic rates were determined. Oxalacetate is the main OAH substrate, but the enzyme also acts as a lyase of (2R,3S)-dimethyl malate with approximately 1000-fold lower efficacy. The crystal structure of OAH was determined alone, in complex with a mechanism-based inhibitor, 3,3-difluorooxalacetate (DFOA), and in complex with the reaction product, oxalate, to a resolution limit of 1.30, 1.55, and 1.65 A, respectively. OAH assembles into a dimer of dimers with each subunit exhibiting an (alpha/beta)(8) barrel fold and each pair swapping the 8th alpha-helix. An active site "gating loop" exhibits conformational disorder in the ligand-free structure. To obtain the structures of the OAH.ligand complexes, the ligand-free OAH crystals were soaked briefly with DFOA or oxalacetate. DFOA binding leads to ordering of the gating loop in a conformation that sequesters the ligand from the solvent. DFOA binds in a gem-diol form analogous to the oxalacetate intermediate/transition state. Oxalate binds in a planar conformation, but the gating loop is largely disordered. Comparison between the OAH structure and that of the closely related enzyme, 2,3-dimethylmalate lyase, suggests potential determinants of substrate preference.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Catalytic Domain
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Fungi / enzymology*
  • Fungi / pathogenicity
  • Hydrolases / chemistry*
  • Hydrolases / genetics
  • Ligands
  • Molecular Sequence Data
  • Plant Diseases / microbiology
  • Protein Conformation
  • Protein Multimerization
  • Substrate Specificity
  • Virulence Factors / chemistry


  • Ligands
  • Virulence Factors
  • Hydrolases
  • oxaloacetase

Associated data

  • GENBANK/GU932672
  • PDB/3LYE
  • PDB/3M0J
  • PDB/3M0K