title: The catabolism of 2,4-xylenol and p-cresol share the enzymes for the oxidation of para-methyl group in Pseudomonas putida NCIMB 9866.
abstract: 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).
authors.affiliation: Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
authors.forename: Yan-Fei
authors.initials: YF
authors.lastname: Chen
authors.forename: Hongjun
authors.initials: H
authors.lastname: Chao
authors.forename: Ning-Yi
authors.initials: NY
authors.lastname: Zhou
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000032:analysis / Q000235:genetics; D002244:Carbon / Q000378:metabolism; D003408:Cresols / Q000378:metabolism*; D004734:Energy Metabolism; D020869:Gene Expression Profiling; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D006899:Mixed Function Oxygenases / Q000032:analysis / Q000235:genetics; D010084:Oxidation-Reduction; D016958:Pseudomonas putida / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D014992:Xylenes / Q000378:metabolism*
chemical_list: D003408:Cresols; D014992:Xylenes; C032538:4-cresol; C027804:2,4-dimethylphenol; D002244:Carbon; D006899:Mixed Function Oxygenases; C049502:4-cresol dehydrogenase (hydroxylating); D000445:Aldehyde Oxidoreductases; C068611:4-hydroxybenzaldehyde dehydrogenase