Bacterial 2,4-dioxygenases: new members of the alpha/beta hydrolase-fold superfamily of enzymes functionally related to serine hydrolases

J Bacteriol. 1999 Sep;181(18):5725-33. doi: 10.1128/JB.181.18.5725-5733.1999.


1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase (Qdo) from Pseudomonas putida 33/1 and 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (Hod) from Arthrobacter ilicis Rü61a catalyze an N-heterocyclic-ring cleavage reaction, generating N-formylanthranilate and N-acetylanthranilate, respectively, and carbon monoxide. Amino acid sequence comparisons between Qdo, Hod, and a number of proteins belonging to the alpha/beta hydrolase-fold superfamily of enzymes and analysis of the similarity between the predicted secondary structures of the 2,4-dioxygenases and the known secondary structure of haloalkane dehalogenase from Xanthobacter autotrophicus GJ10 strongly suggested that Qdo and Hod are structurally related to the alpha/beta hydrolase-fold enzymes. The residues S95 and H244 of Qdo were found to be arranged like the catalytic nucleophilic residue and the catalytic histidine, respectively, of the alpha/beta hydrolase-fold enzymes. Investigation of the potential functional significance of these and other residues of Qdo through site-directed mutagenesis supported the hypothesis that Qdo is structurally as well as functionally related to serine hydrolases, with S95 being a possible catalytic nucleophile and H244 being a possible catalytic base. A hypothetical reaction mechanism for Qdo-catalyzed 2,4-dioxygenolysis, involving formation of an ester bond between the catalytic serine residue and the carbonyl carbon of the substrate and subsequent dioxygenolysis of the covalently bound anionic intermediate, is discussed.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arthrobacter / enzymology
  • Bacteria / enzymology*
  • Dioxygenases*
  • Kinetics
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oxygenases / chemistry*
  • Oxygenases / metabolism
  • Protein Folding
  • Protein Structure, Secondary
  • Pseudomonas putida / enzymology
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Recombinant Proteins
  • Oxygenases
  • 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (decyclizing, CO-forming)
  • Dioxygenases