New bacterial pathway for 4- and 5-chlorosalicylate degradation via 4-chlorocatechol and maleylacetate in Pseudomonas sp. strain MT1

J Bacteriol. 2003 Dec;185(23):6790-800. doi: 10.1128/JB.185.23.6790-6800.2003.


Pseudomonas sp. strain MT1 is capable of degrading 4- and 5-chlorosalicylates via 4-chlorocatechol, 3-chloromuconate, and maleylacetate by a novel pathway. 3-Chloromuconate is transformed by muconate cycloisomerase of MT1 into protoanemonin, a dominant reaction product, as previously shown for other muconate cycloisomerases. However, kinetic data indicate that the muconate cycloisomerase of MT1 is specialized for 3-chloromuconate conversion and is not able to form cis-dienelactone. Protoanemonin is obviously a dead-end product of the pathway. A trans-dienelactone hydrolase (trans-DLH) was induced during growth on chlorosalicylates. Even though the purified enzyme did not act on either 3-chloromuconate or protoanemonin, the presence of muconate cylcoisomerase and trans-DLH together resulted in considerably lower protoanemonin concentrations but larger amounts of maleylacetate formed from 3-chloromuconate than the presence of muconate cycloisomerase alone resulted in. As trans-DLH also acts on 4-fluoromuconolactone, forming maleylacetate, we suggest that this enzyme acts on 4-chloromuconolactone as an intermediate in the muconate cycloisomerase-catalyzed transformation of 3-chloromuconate, thus preventing protoanemonin formation and favoring maleylacetate formation. The maleylacetate formed in this way is reduced by maleylacetate reductase. Chlorosalicylate degradation in MT1 thus occurs by a new pathway consisting of a patchwork of reactions catalyzed by enzymes from the 3-oxoadipate pathway (catechol 1,2-dioxygenase, muconate cycloisomerase) and the chlorocatechol pathway (maleylacetate reductase) and a trans-DLH.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Carboxylic Ester Hydrolases / antagonists & inhibitors
  • Carboxylic Ester Hydrolases / metabolism
  • Catechol 1,2-Dioxygenase
  • Catechols / metabolism*
  • Dioxygenases*
  • Furans / analysis
  • Furans / metabolism
  • Genome, Bacterial
  • Intramolecular Lyases / metabolism
  • Maleates / analysis
  • Maleates / metabolism*
  • Molecular Sequence Data
  • Multienzyme Complexes / metabolism*
  • Oxidoreductases Acting on CH-CH Group Donors / metabolism
  • Oxygenases / metabolism
  • Pseudomonas / genetics
  • Pseudomonas / metabolism*
  • Salicylates / metabolism*
  • Sequence Homology, Amino Acid
  • Xenobiotics / metabolism


  • Catechols
  • Furans
  • Maleates
  • Multienzyme Complexes
  • Salicylates
  • Xenobiotics
  • maleoylacetic acid
  • 4-chlorosalicylic acid
  • protoanemonin
  • Oxygenases
  • Dioxygenases
  • Catechol 1,2-Dioxygenase
  • Oxidoreductases Acting on CH-CH Group Donors
  • maleylacetate reductase
  • Carboxylic Ester Hydrolases
  • carboxymethylenebutenolidase
  • Intramolecular Lyases
  • muconate cycloisomerase
  • 4-chlorocatechol
  • 5-chlorosalicylic acid