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 → Nitroaromatic Compounds Degradation → Nitrotoluene Degradation|
Some taxa known to possess this pathway include : Acidovorax sp. JS42
Expected Taxonomic Range:
Nitroaromatic compounds such as nitrophenols, nitrotoluenes and nitrobenzoates, are used in the synthesis of pesticides, plasticizers, dyes, pharmaceuticals, and explosives. These compounds are contaminants of waste waters, rivers and groundwater, and of the atmosphere [Leuenberger88]. In most cases nitroaromatic compounds are highly toxic to living organisms, and several of them have been listed as priority pollutants by the U.S. Environmental Protection Agency [Callahan79].
Despite their toxicity, these compounds can be degraded by several microorganisms. These degradation pathways almost always start with the removal or replacement of the nitro group [MarvinSikkema94]. The mechanisms in which bacteria are able to remove the nitro group can be divided into two broad categories - oxidative and reductive. In oxidative pathways the nitro group is released in the form of nitrite, usually catalyzed by a mono- or di-oxygenase enzymes. For examples, see 2-nitrotoluene degradation and 4-Nitrotoluene Degradation. In reductive pathways the nitro group is reduced via a nitroso intermediate to a hydroxylamino group, and sometime further to an amino group, and is released in the form of ammonia. For examples see 4-nitrotoluene degradation II and 4-nitrobenzoate degradation.
About This Pathway
Acidovorax sp. JS42 is a proteobacterium that was isolated from nitrobenzene-contaminated soil and groundwater. The organism can grow on 2-nitrotoluene as the sole source of carbon, nitrogen, and energy. 2-nitrotoluene is rapidly metabolized during growth with concomitant release of nitrite [Haigler94].
Extracts prepared from cells grown with 2-nitrotoluene oxidize the compoud to 3-methylcatechol and nitrite in the presence of NAD(P)H and ferrous iron [An94]. 2-nitrotoluene dioxygenase, the enzyme responsible for this reaction, is a three component dioxygenase system and has been purified and well characterized [An94, Parales98, Parales05]. The enzymatic activities of other two enzymes of the pathway, 3-methylcatechol 2,3-dioxygenase and 2-hydroxy-6-oxohepta-2,4-dienoate hydrolase, were demonstrated in the extracts, but the enzymes have not been purified, and the enzymes are not well characterized [Haigler94].
An94: An D, Gibson DT, Spain JC (1994). "Oxidative release of nitrite from 2-nitrotoluene by a three-component enzyme system from Pseudomonas sp. strain JS42." J Bacteriol 176(24);7462-7. PMID: 8002568
Callahan79: Callahan, M. A., Slimak, M. W., Gabel, N. W., May, J. P., Fowler, C. F., Freed, J. R., Jennings, P., Durfee, R. L., Whitmore, F. C., Maestri, B., Mabey, W. R., Holt, B. R., Gould, C. (1979). "Water-related environmental fate of 129 priority pollutants." EPA report-440/4-79-029b. U.S. Environmental Protection Agency, Washington, D.C.
Parales05: Parales RE, Huang R, Yu CL, Parales JV, Lee FK, Lessner DJ, Ivkovic-Jensen MM, Liu W, Friemann R, Ramaswamy S, Gibson DT (2005). "Purification, characterization, and crystallization of the components of the nitrobenzene and 2-nitrotoluene dioxygenase enzyme systems." Appl Environ Microbiol 71(7);3806-14. PMID: 16000792
Parales98: Parales JV, Parales RE, Resnick SM, Gibson DT (1998). "Enzyme specificity of 2-nitrotoluene 2,3-dioxygenase from Pseudomonas sp. strain JS42 is determined by the C-terminal region of the alpha subunit of the oxygenase component." J Bacteriol 180(5);1194-9. PMID: 9495758
Furukawa93b: 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
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
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
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
Okuta04: Okuta A, Ohnishi K, Harayama S (2004). "Construction of chimeric catechol 2,3-dioxygenase exhibiting improved activity against the suicide inhibitor 4-methylcatechol." Appl Environ Microbiol 70(3);1804-10. PMID: 15006807
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
Shields95: Shields MS, Reagin MJ, Gerger RR, Campbell R, Somerville C (1995). "TOM, a new aromatic degradative plasmid from Burkholderia (Pseudomonas) cepacia G4." Appl Environ Microbiol 1995;61(4);1352-6. PMID: 7538275
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
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