Pseudomonas pseudoalcaligenes JS45 can grow with nitrobenzene as the sole source of carbon, nitrogen, and energy. The strategy the bacterium uses in this pathway is to reduce the nitroaromatic first to make it more susceptible to degradation by a dioxygenase reaction. The last compound shown in this branch of the pathway, 2-aminomuconic semialdehyde, disappears from cell extracts in a NAD+-dependent reaction (Nishino and Spain, 1993). Comamonas sp. CNB-1 and other organisms can degrade 4-chloronitrobenzene by a very similar pathway (Ma et al., 2007).
Comamonas sp. JS765 can also use nitrobenzene as the sole source of carbon, nitrogen, and energy. It inserts dioxygen directly into nitrobenzene, with concomitant reduction of the substrate to form catechol (Nishino and Spain (1995) Applied and Environmental Microbiology 61:2308-2313). Aniline also is degraded to catechol in a similar manner by Delftia sp. AN3 (Liu et al., 2002), and this reaction, catalyzed by aniline dioxygenase, has been added to the nitrobenzene pathway. Rhodococcus erythropolis AN-13, Pseudomonas putida mt-2, Moraxella sp. strain G., and Hydrogenophaga palleronii S5 can also carry out this reaction (Takenaka et al., 2003).
The following is a text-format nitrobenzene degradation pathway map. Organisms which can initiate the pathway are given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions. This map is also available in graphic (17k) format.
Nitrobenzene Nitrobenzene Pseudomonas pseudoalcaligenes Comomonas sp. JS45 Aniline JS765 | nitrobenzene Delftia sp. AN3 | nitrobenzene | nitroreductase and others | 1,2-dioxygenase | | | v | v from the Nitrosobenzene +----------> Catechol <------ NAPH, BENZ2, HCH, ABZ2, PPC, PBA, ANT2, VAN | aniline | pathways | dioxygenase | | nitrobenzene | | nitroreductase |------------------------+ | | | v | catechol | catechol Hydroxylaminobenzene | 2,3-dioxygenase | 1,2-dioxygenase | | | | hydroxyl- v v | aminobenzene 2-Hydroxymuconic cis,cis-Muconate | mutase semialdehyde | | | | v | 2-hydroxymuconate | 2-Aminophenol | semialdehyde | | | hydrolase | | 2-aminophenol v v | 1,6-dioxygenase cis-2-Hydroxy- Intermediary | penta-2,4-dienoate Metabolism v | (KEGG) 2-Aminomuconic semialdehyde | 2-oxopent- | | 4-enoate | | hydratase | v | 4-Hydroxy- | 2-oxovalerate v | Intermediary | 4-hydroxy- Metabolism | 2-oxo- (KEGG) | valerate | aldolase |------------------------+ | | v v Pyruvate Acetaldehyde | | | | | | v v Intermediary Intermediary Metabolism Metabolism (KEGG) (KEGG)
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