Trichloroethylene (TCE) is a good solvent and is used in manufacturing to clean grease from machinery. It is one of the most abundant environmental pollutants of groundwater in the United States. In some groundwater, TCE undergoes reductive dechlorination catalyzed by anaerobic bacteria that yields vinyl chloride, a potent human carcinogen. TCE removal by dumping or air stripping is now largely disallowed and this has focused efforts on biological methods of TCE remediation in soil and water.
The enzyme that starts one branch of this pathway, toluene 1,2-dioxygenase, has many other catalytic abilities, which are documented in a table of the Reactions of Toluene 1,2-Dioxygenase.
The spontaneous degradation of trichloroethylene epoxide can produce as many as four products: dichloroacetate, carbon monoxide, glyoxylate, and formate. The number, type, and proportion of products seen depends on the local environment.
The following is a text-format trichloroethylene 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 (16k) format.
TCE TCE TCE TCE TCE Methylosinus Methylosinus Burkholderia Ps. Ps. trichosporium trichosporium cepacia G4 putida F1 putida F1 OB3b OB3b | | | | | | | | | soluble | sMMO | toluene toluene | toluene | | methane | | 2-monooxygenase dioxygenase | dioxygenase | | monooxygenase | | | | | (sMMO) | | | | | | | v v | | | Glyoxylate Formate | | | | | | | | | | v v v v v Chloral Trichloroethylene epoxide Intermediary to the hydrate (TCE epoxide) Metabolism C1 Metabolic | | (KEGG) Cycle | | | From the | +---------------+ Trichloroethane | spontaneous | | Pathway | | | | | | | dehydro- | dehydro- | +----------------+--------------+--------------+ | genase | genase | | | | | | | | | B | C | D | E v v | | | | | Trichloro- A Trichloro- <--+ | v | | acetate <---> ethanol | | | | Pseudomonas v v v v sp. Dichloroacetate CO Glyoxylate Formate | Pseudomonas sp. | | | | | | | | +------------+ | v v v | | | to the Intermediary to the | strain | strain | Thiocyanate Metabolism C1 Metabolic v PP3, | 113 | Pathway (KEGG) Cycle | K5/5 | haloacid | dichloro- | E2 | dehalogenase | acetate | | | halidohyrolase v v v CO2 Oxalate Glyoxylate | | | | | | v v Intermediary Intermediary Metabolism Metabolism (KEGG) (KEGG)
Page Author(s): Mark Whittaker, David Monroe, Dong Jun Oh and Sean Anderson
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