The catabolism of 2,4-xylenol and p-cresol share the enzymes for the oxidation of para-methyl group in Pseudomonas putida NCIMB 9866

Appl Microbiol Biotechnol. 2014 Feb;98(3):1349-56. doi: 10.1007/s00253-013-5001-z. Epub 2013 Jun 5.


Pseudomonas putida NCIMB 9866 utilizes p-cresol or 2,4-xylenol as a sole carbon and energy source. Enzymes catalyzing the oxidation of the para-methyl group of p-cresol have been studied in detail. However, those responsible for the oxidation of the para-methyl group in 2,4-xylenol catabolism are still not reported. In this study, real-time quantitative PCR analysis indicated pchC- and pchF-encoded p-cresol methylhydroxylase (PCMH) and pchA-encoded p-hydroxybenzaldehyde dehydrogenase (PHBDD) in p-cresol catabolism were also likely involved in the catabolism of 2,4-xylenol. Enzyme activity assays and intermediate identification indicated that the PCMH and PHBDD catalyzed the oxidations of 2,4-xylenol to 4-hydroxy-3-methylbenzaldehyde and 4-hydroxy-3-methylbenzaldehyde to 4-hydroxy-3-methylbenzoic acid, respectively. Furthermore, the PCMH-encoding gene pchF was found to be necessary for the catabolism of 2,4-xylenol, whereas the PHBDD-encoding gene pchA was not essential for the catabolism by gene knockout and complementation. Analyses of the maximum specific growth rate (μ m) and specific activity of the gene-knockout strain to different intermediates revealed the presence of other enzyme(s) with PHBDD activity in strain 9866. However, PHBDD played a major role in the catabolism of 2,4-xylenol in contrast to the other enzyme(s).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aldehyde Oxidoreductases / analysis
  • Aldehyde Oxidoreductases / genetics
  • Carbon / metabolism
  • Cresols / metabolism*
  • Energy Metabolism
  • Gene Expression Profiling
  • Gene Knockout Techniques
  • Genetic Complementation Test
  • Metabolic Networks and Pathways / genetics*
  • Mixed Function Oxygenases / analysis
  • Mixed Function Oxygenases / genetics
  • Oxidation-Reduction
  • Pseudomonas putida / enzymology*
  • Pseudomonas putida / growth & development
  • Pseudomonas putida / metabolism*
  • Real-Time Polymerase Chain Reaction
  • Xylenes / metabolism*


  • Cresols
  • Xylenes
  • 4-cresol
  • 2,4-dimethylphenol
  • Carbon
  • Mixed Function Oxygenases
  • 4-cresol dehydrogenase (hydroxylating)
  • Aldehyde Oxidoreductases
  • 4-hydroxybenzaldehyde dehydrogenase