A gene cluster involved in degradation of substituted salicylates via ortho cleavage in Pseudomonas sp. strain MT1 encodes enzymes specifically adapted for transformation of 4-methylcatechol and 3-methylmuconate

J Bacteriol. 2007 Mar;189(5):1664-74. doi: 10.1128/JB.01192-06. Epub 2006 Dec 15.


Pseudomonas sp. strain MT1 has recently been reported to degrade 4- and 5-chlorosalicylate by a pathway assumed to consist of a patchwork of reactions comprising enzymes of the 3-oxoadipate pathway. Genes encoding the initial steps in the degradation of salicylate and substituted derivatives were now localized and sequenced. One of the gene clusters characterized (sal) showed a novel gene arrangement, with salA, encoding a salicylate 1-hydroxylase, being clustered with salCD genes, encoding muconate cycloisomerase and catechol 1,2-dioxygenase, respectively, and was expressed during growth on salicylate and chlorosalicylate. A second gene cluster (cat), exhibiting the typical catRBCA arrangement of genes of the catechol branch of the 3-oxoadipate pathway in Pseudomonas strains, was expressed during growth on salicylate. Despite their high sequence similarities with isoenzymes encoded by the cat gene cluster, the catechol 1,2-dioxygenase and muconate cycloisomerase encoded by the sal cluster showed unusual kinetic properties. Enzymes were adapted for turnover of 4-chlorocatechol and 3-chloromuconate; however, 4-methylcatechol and 3-methylmuconate were identified as the preferred substrates. Investigation of the substrate spectrum identified 4- and 5-methylsalicylate as growth substrates, which were effectively converted by enzymes of the sal cluster into 4-methylmuconolactone, followed by isomerization to 3-methylmuconolactone. The function of the sal gene cluster is therefore to channel both chlorosubstituted and methylsubstituted salicylates into a catechol ortho cleavage pathway, followed by dismantling of the formed substituted muconolactones through specific pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Catechol 1,2-Dioxygenase / metabolism
  • Catechols / metabolism*
  • Intramolecular Lyases / isolation & purification
  • Intramolecular Lyases / metabolism
  • Mixed Function Oxygenases / isolation & purification
  • Molecular Sequence Data
  • Multigene Family*
  • Pseudomonas / genetics*
  • Pseudomonas / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Salicylates / metabolism*
  • Sorbic Acid / analogs & derivatives
  • Sorbic Acid / metabolism


  • Catechols
  • Salicylates
  • 4-methylcatechol
  • muconic acid
  • Mixed Function Oxygenases
  • Catechol 1,2-Dioxygenase
  • salicylate 1-monooxygenase
  • Intramolecular Lyases
  • muconate cycloisomerase
  • Sorbic Acid

Associated data

  • GENBANK/AY944685
  • GENBANK/DQ870624