This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Aromatic Compounds Degradation → Toluenes Degradation|
Some taxa known to possess this pathway include : Pseudomonas putida F1
Expected Taxonomic Range: Proteobacteria
Toluene is widely used as an industrial additive and solvent. Toluene and related aromatic compounds can be degraded by bacteria, and have been studied in the metabolically versatile genus Pseudomonas and closely related genera. These studies have been directed toward bioremediation of environmental pollutants by metabolic engineering, and the development of syntrophic bacterial consortia (reviewed in [Diaz04]). Aerobic pathways of toluene degradation have been identified in various species that involve different initial monooxygenase, or hydroxylating dioxygenase reactions. Several of these pathways converge in the formation of 2,3-dihydroxytoluene (3-methylcatechol) [Shields91]. This compound is a substrate for ring cleavage enzymes, the products of which are metabolized via a common meta fission pathway, resulting in the formation of compounds of central metabolism (see this pathway and MetaCyc pathways toluene degradation to 2-oxopent-4-enoate (via 4-methylcatechol) and toluene degradation to 2-oxopent-4-enoate I (via o-cresol)).
The chromosome of Pseudomonas putida F1 contains a gene cluster encoding enzymes that allow this organism to grow on toluene and related compounds as sole carbon and energy source [Zylstra89, Menn91, Lau94]. Other strains of P. putida may contain plasmid-encoded genes for toluene degradation (see MetaCyc pathway toluene degradation to benzoate). The inducible toluene dioxygenase enzyme hydroxylates toluene to its dihydrodiol derivative by incorporating both atoms of an oxygen molecule into the aromatic nucleus. The dihydroxylated derivative is dehydrogenated to a catechol. Ring fission of the catechol 2,3-dihydroxytoluene (3-methylcatechol) is catalyzed by catechol 2,3-dioxygenase to produce cis,cis-2-hydroxy-6-oxohepta-2,4-dienoate. This compound is hydrolyzed to 2-oxopent-4-enoate, or its tautomeric dienol form cis-2-hydroxypenta-2,4-dienoate. This tautomerization occurs spontaneously in aqueous solution [Johnson04]. It is not known which tautomeric form is produced by the hydrolase, and which form is used by the hydratase of P. putida F1 in this pathway. However, it has been suggested that the Pseudomonas putida mt-2 hydratase, encoded by the TOL plasmid pWW0, uses the dienol form as a substrate [Harayama89], and there is evidence that the Escherichia coli hydratase also uses the dienol form as substrate, producing a ketonized intermediate in the reaction mechanism [Pollard98]. The products of the pathway are pyruvate, which enters central metabolism, and acetaldehyde, which may be converted by acylating aldehyde dehydrogenase to acetyl-CoA, a central metabolite [Lau94].
Superpathways: superpathway of aerobic toluene degradation
Variants: 2,4-xylenol degradation to protocatechuate, 4-methylphenol degradation to protocatechuate, toluene degradation I (aerobic) (via o-cresol), toluene degradation II (aerobic) (via 4-methylcatechol), toluene degradation III (aerobic) (via p-cresol), toluene degradation IV (aerobic) (via catechol), toluene degradation to 2-oxopent-4-enoate (via 4-methylcatechol), toluene degradation to 2-oxopent-4-enoate I (via o-cresol), toluene degradation to 4-methylphenol, toluene degradation to benzoate, toluene degradation to benzoyl-CoA (anaerobic), toluene degradation VI (anaerobic)
Harayama89: Harayama S, Rekik M, Ngai KL, Ornston LN (1989). "Physically associated enzymes produce and metabolize 2-hydroxy-2,4-dienoate, a chemically unstable intermediate formed in catechol metabolism via meta cleavage in Pseudomonas putida." J Bacteriol 171(11);6251-8. PMID: 2681159
Johnson04: Johnson WH, Wang SC, Stanley TM, Czerwinski RM, Almrud JJ, Poelarends GJ, Murzin AG, Whitman CP (2004). "4-Oxalocrotonate tautomerase, its homologue YwhB, and active vinylpyruvate hydratase: synthesis and evaluation of 2-fluoro substrate analogues." Biochemistry 43(32);10490-501. PMID: 15301547
Johnson06: Johnson DR, Park J, Kukor JJ, Abriola LM (2006). "Effect of carbon starvation on toluene degradation activity by toluene monooxygenase-expressing bacteria." Biodegradation NIL;1-9. PMID: 16477358
Lau94: Lau PC, Bergeron H, Labbe D, Wang Y, Brousseau R, Gibson DT (1994). "Sequence and expression of the todGIH genes involved in the last three steps of toluene degradation by Pseudomonas putida F1." Gene 1994;146(1);7-13. PMID: 8063106
Menn91: Menn FM, Zylstra GJ, Gibson DT (1991). "Location and sequence of the todF gene encoding 2-hydroxy-6-oxohepta-2,4-dienoate hydrolase in Pseudomonas putida F1." Gene 1991;104(1);91-4. PMID: 1916282
Pollard98: Pollard JR, Bugg TD (1998). "Purification, characterisation and reaction mechanism of monofunctional 2-hydroxypentadienoic acid hydratase from Escherichia coli." Eur J Biochem 251(1-2);98-106. PMID: 9492273
Shields91: Shields MS, Montgomery SO, Cuskey SM, Chapman PJ, Pritchard PH (1991). "Mutants of Pseudomonas cepacia G4 defective in catabolism of aromatic compounds and trichloroethylene." Appl Environ Microbiol 57(7);1935-41. PMID: 1892384
Zylstra89: Zylstra GJ, Gibson DT (1989). "Toluene degradation by Pseudomonas putida F1. Nucleotide sequence of the todC1C2BADE genes and their expression in Escherichia coli." J Biol Chem 264(25);14940-6. PMID: 2670929
Ferrandez97: Ferrandez A, Garcia JL, Diaz E (1997). "Genetic characterization and expression in heterologous hosts of the 3-(3-hydroxyphenyl)propionate catabolic pathway of Escherichia coli K-12." J Bacteriol 1997;179(8);2573-81. PMID: 9098055
Fischer13: Fischer B, Boutserin S, Mazon H, Collin S, Branlant G, Gruez A, Talfournier F (2013). "Catalytic properties of a bacterial acylating acetaldehyde dehydrogenase: evidence for several active oligomeric states and coenzyme A activation upon binding." Chem Biol Interact 202(1-3);70-7. PMID: 23237860
Furukawa93: Furukawa K, Hirose J, Suyama A, Zaiki T, Hayashida S (1993). "Gene components responsible for discrete substrate specificity in the metabolism of biphenyl (bph operon) and toluene (tod operon)." J Bacteriol 175(16);5224-32. PMID: 8349562
Gupta00: Gupta S, Mat-Jan F, Latifi M, Clark DP (2000). "Acetaldehyde dehydrogenase activity of the AdhE protein of Escherichia coli is inhibited by intermediates in ubiquinone synthesis." FEMS Microbiol Lett 182(1);51-5. PMID: 10612730
He99: He Z, Spain JC (1999). "Comparison of the downstream pathways for degradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45 (2-aminophenol pathway) and by Comamonas sp. JS765 (catechol pathway)." Arch Microbiol 171(5);309-16. PMID: 10382261
Hugo00: Hugo N, Meyer C, Armengaud J, Gaillard J, Timmis KN, Jouanneau Y (2000). "Characterization of three XylT-like [2Fe-2S] ferredoxins associated with catabolism of cresols or naphthalene: evidence for their involvement in catechol dioxygenase reactivation." J Bacteriol 182(19);5580-5. PMID: 10986264
Jiang96a: Jiang H, Parales RE, Lynch NA, Gibson DT (1996). "Site-directed mutagenesis of conserved amino acids in the alpha subunit of toluene dioxygenase: potential mononuclear non-heme iron coordination sites." J Bacteriol 178(11);3133-9. PMID: 8655491
Jiang99: Jiang H, Parales RE, Gibson DT (1999). "The alpha subunit of toluene dioxygenase from Pseudomonas putida F1 can accept electrons from reduced FerredoxinTOL but is catalytically inactive in the absence of the beta subunit." Appl Environ Microbiol 65(1);315-8. PMID: 9872799
Kazahaya72: Kazahaya, T., Kawai, K., Yashima, S., Sasaki, Y. (1972). "Aerobic dissimilation of glucose by heterolactic bacteria III. Aldehyde dehydrogenase And alcohol dehydrogenase of Leuconostoc mesenteroides." J. Gen. Appl. Microbiol. 18:43-55.
Kessler91: Kessler D, Leibrecht I, Knappe J (1991). "Pyruvate-formate-lyase-deactivase and acetyl-CoA reductase activities of Escherichia coli reside on a polymeric protein particle encoded by adhE." FEBS Lett 281(1-2);59-63. PMID: 2015910
Kukor91: Kukor JJ, Olsen RH (1991). "Genetic organization and regulation of a meta cleavage pathway for catechols produced from catabolism of toluene, benzene, phenol, and cresols by Pseudomonas pickettii PKO1." J Bacteriol 1991;173(15);4587-94. PMID: 1856161
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