Comamonas testosteroni BR6020 possesses a single genetic locus for extradiol cleavage of protocatechuate

Microbiology (Reading). 2001 Aug;147(Pt 8):2157-2167. doi: 10.1099/00221287-147-8-2157.


A key intermediate for biodegradation of various distinct aromatic growth substrates in Comamonas testosteroni is protocatechuate (Pca), which is metabolized by the 4,5-extradiol (meta) ring fission pathway. A locus harbouring genes from C. testosteroni BR6020 was cloned, dubbed pmd, which encodes the enzymes that degrade Pca. The identity of pmdAB, encoding respectively the alpha- and beta-subunit of the Pca ring-cleavage enzyme, was confirmed by N-terminal sequencing and molecular mass determination of both subunits from the separated enzyme. Disruption of pmdA resulted in a strain unable to grow on Pca and a variety of aromatic substrates funnelled through this compound (m- and p-hydroxybenzoate, p-sulfobenzoate, phthalate, isophthalate, terephthalate, vanillate, isovanillate and veratrate). Growth on benzoate and o-aminobenzoate (anthranilate) was not affected in this strain, indicating that these substrates are metabolized via a different lower pathway. Tentative functions for the products of other pmd genes were assigned based on sequence identity and/or similarity to proteins from other proteobacteria involved in uptake or metabolism of aromatic compounds. This study provides evidence for a single lower pathway in C. testosteroni for metabolism of Pca, which is generated by different upper pathways acting on a variety of aromatic substrates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Biodegradation, Environmental
  • Cloning, Molecular
  • Comamonas testosteroni / enzymology*
  • Comamonas testosteroni / genetics*
  • Culture Media
  • Dioxygenases*
  • Hydrocarbons, Aromatic / metabolism
  • Hydroxybenzoates / metabolism*
  • Molecular Sequence Data
  • Oxygenases / chemistry
  • Oxygenases / genetics*
  • Oxygenases / metabolism
  • Sequence Analysis, DNA


  • Culture Media
  • Hydrocarbons, Aromatic
  • Hydroxybenzoates
  • protocatechuic acid
  • Oxygenases
  • Dioxygenases
  • protocatechuate 4,5-dioxygenase

Associated data

  • GENBANK/AF305325