Chlorobenzene Pathway Map

Although chlorobenzene is not formed in any significant quantity naturally, the United States chemical industry synthesized 231 million pounds of chlorobenzene in 1992 alone. Chlorobenzene is commonly used in the manufacture of nitrochlorobenzenes, phenol, aniline, and other industrial chemicals. It also functions as a paint solvent, heat-transfer medium, and an intermediate compound in the manufacture of some pesticides. Most chlorobenzene that is discharged into the environment quickly evaporates and is subsequently degraded atmospherically via reactions with photochemically-generated hydroxyl radicals. Enzymes involved in the microbial degradation of chlorobenzene are believed to have evolved from simliar enzymes catalyzing the degradation of benzene and toluene (Werlen et al., 1996).

The Japanese Database for Environmental Fate of Chemicals has information on the rates and pathways of Biodegradation of Chlorophenols and Chlorobenzenes in Sediments.

2-Chlorophenol is hydroxylated to form 3-chlorocatechol in several Rhodococcus spp. (Finkel'shtein et al., 2000), Trichosporon cutaneum, T. beigelii and Cryptococcus elinovii (Kälin et al., 1992).

The following is a text-format chlorobenzene 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 (7k) format.

                                                               from the
                              Chlorobenzene <------------- Beta-HCH Pathway             
                             Pseudomonas sp. 
                          P51, JS150, RHO1, JS6
                                    |
                                    |    
                                    | chlorobenzene dioxygenase 
                                    |
                                    |
                                    v    
  2-Chlorophenol       3-Chloro-cis-1,2-dihydroxy-     
 R. opacus 1G, 1cp         cyclohexa-3,5-diene
  R. rhodnii 135                    |
    and others                      |
         | phenol                   | cis-1,2-dihydrobenzene-
         | 2-monooxygenase          | 1,2-diol dehydrogenase 
         |                          |
         |                          |
         |                          v
         +-----------------> 3-Chlorocatechol --------------------+    
                                    |                             |
                                    |                             |
                                    | catechol 1,2-               | 2,3-dihydroxybiphenyl 
                                    | dioxygenase                 | 1,2-dioxygenase 
                                    |                             |
                                    |                             |
                                    v                             v
                        2-Chloro-cis,cis-muconate      3-chloro-2-hydroxymuconic
                                    |                        semialdehyde
                                    |
                                    | chloromuconate
                                    | cycloisomerase
                                    |
                                    | 
                                    v
                         trans-4-Carboxymethyl-
                           enebut-2-en-4-olide
                                    |
                                    |
                                    | dienelactone hydrolase
                                    |
                                    |
                                    v                      from the
 	                      Maleylacetate <--- 4-Carboxy-4'-sulfoazobenzene
                                    |                       Pathway
                                    |
                                    |
                                    | maleylacetate reductase
                                    |
                                    |
                                    v
	                      3-Oxoadipate
                                    |
                                    |
                                    |
                                    v
                              Intermediary
                               Metabolism
                                 (KEGG)  

Page Author(s): Ryan McLeish and Michael Turnbull

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