Characterization of the hca cluster encoding the dioxygenolytic pathway for initial catabolism of 3-phenylpropionic acid in Escherichia coli K-12

J Bacteriol. 1998 Jun;180(11):2915-23. doi: 10.1128/JB.180.11.2915-2923.1998.


We have identified, cloned, and sequenced the hca cluster encoding the dioxygenolytic pathway for initial catabolism of 3-phenylpropionic acid (PP) in Escherichia coli K-12. This cluster maps at min 57.5 of the chromosome and is composed of five catabolic genes arranged as a putative operon (hcaA1A2CBD) and two additional genes transcribed in the opposite direction that encode a potential permease (hcaT) and a regulator (hcaR). Sequence comparisons revealed that while hcaA1A2CD genes encode the four subunits of the 3-phenylpropionate dioxygenase, the hcaB gene codes for the corresponding cis-dihydrodiol dehydrogenase. This type of catabolic module is homologous to those encoding class IIB dioxygenases and becomes the first example of such a catabolic cluster in E. coli. The inducible expression of the hca genes requires the presence of the hcaR gene product, which acts as a transcriptional activator and shows significant sequence similarity to members of the LysR family of regulators. Interestingly, the HcaA1A2CD and HcaB enzymes are able to oxidize not only PP to 3-(2,3-dihydroxyphenyl)propionate (DHPP) but also cinnamic acid (CI) to its corresponding 2, 3-dihydroxy derivative. Further catabolism of DHPP requires the mhp-encoded meta fission pathway for the mineralization of 3-hydroxyphenylpropionate (3HPP) (A. Ferrández, J. L. García, and E. Díaz, J. Bacteriol. 179:2573-2581, 1997). Expression in Salmonella typhimurium of the mhp genes alone or in combination with the hca cluster allowed the growth of the recombinant bacteria in 3-hydroxycinnamic acid (3HCI) and CI, respectively. Thus, the convergent mhp- and hca-encoded pathways are also functional in S. typhimurium, and they are responsible for the catabolism of different phenylpropanoid compounds (3HPP, 3HCI, PP, and CI) widely available in nature.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • Constitutive Androstane Receptor
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins*
  • Genes, Bacterial / genetics*
  • Membrane Transport Proteins / genetics
  • Models, Chemical
  • Molecular Sequence Data
  • Multigene Family / genetics*
  • Organic Anion Transporters*
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism
  • Oxygenases / genetics*
  • Oxygenases / metabolism
  • Phenylpropionates / metabolism*
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Restriction Mapping
  • Sequence Analysis, DNA
  • Trans-Activators / genetics
  • Transcription Factors*


  • Constitutive Androstane Receptor
  • Escherichia coli Proteins
  • HcaB protein, E coli
  • HcaT protein, E coli
  • Membrane Transport Proteins
  • Organic Anion Transporters
  • Phenylpropionates
  • Receptors, Cytoplasmic and Nuclear
  • Trans-Activators
  • Transcription Factors
  • 3-phenylpropionic acid
  • Oxidoreductases
  • Oxygenases
  • 3-phenylpropionate dioxygenase

Associated data

  • GENBANK/Y11070
  • GENBANK/Y11071