Functional characterization and molecular modeling of methylcatechol 2,3-dioxygenase from o-xylene-degrading Rhodococcus sp. strain DK17

Biochem Biophys Res Commun. 2005 Jan 28;326(4):880-6. doi: 10.1016/j.bbrc.2004.11.123.


Rhodococcus sp. strain DK17 is known to metabolize o-xylene and toluene through the intermediates 3,4-dimethylcatechol and 3- and 4-methylcatechol, respectively, which are further cleaved by a common catechol 2,3-dioxygenase. A putative gene encoding this enzyme (akbC) was amplified by PCR, cloned, and expressed in Escherichia coli. Assessment of the enzyme activity expressed in E. coli combined with sequence analysis of a mutant gene demonstrated that the akbC gene encodes the bona fide catechol 2,3-dioxygenase (AkbC) for metabolism of o-xylene and alkylbenzenes such as toluene and ethylbenzene. Analysis of the deduced amino acid sequence indicates that AkbC consists of a new catechol 2,3-dioxygenase class specific for methyl-substituted catechols. A computer-aided molecular modeling studies suggest that amino acid residues (particularly Phe177) in the beta10-beta11 loop play an essential role in characterizing the substrate specificity of AkbC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Biodegradation, Environmental
  • Catechol 2,3-Dioxygenase
  • Dioxygenases / analysis
  • Dioxygenases / chemistry*
  • Dioxygenases / metabolism*
  • Enzyme Activation
  • Models, Molecular*
  • Molecular Sequence Data
  • Protein Conformation
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Rhodococcus / classification
  • Rhodococcus / enzymology*
  • Sequence Homology, Amino Acid
  • Species Specificity
  • Structure-Activity Relationship
  • Xylenes / metabolism*


  • Recombinant Proteins
  • Xylenes
  • Dioxygenases
  • Catechol 2,3-Dioxygenase
  • 2-xylene