Fluorinated hydrocarbons are most commonly used in herbicides, fungicides, and pharmaceuticals. A study dedicated to the isolation and characterization of aromatic compound degrading microbes found 4-fluorobenzoate in freshwater sediment and sewage in concentrations of 50-500 ppm (Horowitz, et al. (1982) Dev Ind Microbiol 23:435-44). Toxicology information is limited for this particular compound but studies on other more common halobenzenes have shown toxicity in high doses.
Knowledge of fluorobenzoate metabolism is relatively sparse in comparison to other halobenzoates. Fluorinated organic compounds, such as 4-fluorobenzoate, are more resistant to microbial degradation than other halogenated compounds due to unusual carbon-fluorine bond properties (Giesy et al., 2001). Aerobic metabolism of 4-fluorobenzoate is initiated by an oxygen-dependent ring cleavage in B. cepacia , Pseudomonas sp. B13, A. eutrophus JMP134 and A. eutrophus 335. Cycloisomerization of 3-fluoro-cis,cis-muconate with the addition of a proton yields 4-fluoromuconolactone as the sole major product. Lactone hydrolysis preceeds a secondary dehalogenation reaction and the resulting product enters intermediary metabolism through the TCA cycle (Schlomann et al., 1990). In contrast to chloride and bromide elimination through a carbanionic intermediate (Schreiber et al., 1980), defluorination is not coupled to cycloisomerization and dienelactone formation is negligible (Schlomann et al., 1990).
4-Fluorobenzoate is anaerobically degraded by Aureobacterium sp. strain RHO25. Coenzyme A ligation and dehalogenation yields 4-hydroxybenzoyl-CoA, which enters common intermediary metabolism (Oltmanns et al., 1989). These pathways may be relevant for the degradation of other fluoroaromatic compounds.
The following is a text-format 4-fluorobenzoate 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 (12k) format.
4-Fluorobenzoate 4-Fluorobenzoate
Pseudomonas sp. B13 Aureobacterium sp. RHO25
Burkholderia cepacia |
Alcaligenes eutrophus 335 & JMP134 |
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| |
benzoate | | 4-chlorobenzoate-CoA
dioxygenase | | ligase
| |
| |
| |
v v
4-Fluorocyclohexadiene- 4-Fluorobenzoyl-CoA
cis,cis-1,2-diol-carboxylate |
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| |
3,5-cyclohexadiene- | |
1,2-diol-1- | | 4-chlorobenzoyl-CoA
carboxylate | | dehalogenase
dehydrogenase | |
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| |
from the v v
3-Fluorobenzoate----> 4-Fluorocatechol 4-Hydroxybenzoyl-CoA
Pathway | |
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catechol | |
1,2-dioxygenase | |
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| v
v to the
3-Fluoro-cis,cis-muconate 2,4-Dichlorobenzoate
| Pathway
|
muconate |
cycloisomerase |
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|
v
4-Fluoromuconolactone
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dienelactone |
hydrolase v
|
|
|
v
Maleylacetate
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|
|
|
v
Intermediary
Metabolism
(KEGG)
Page Author(s): Michael J. Turnbull
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