Bromoxynil (an/aerobic) Pathway Map

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This pathway was contributed by William C. Ford, BioC/MicE 5309, University of Minnesota.

Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) is a herbicide used for post-emergent control of annual broadleaf weeds by inhibiting photosynthesis in the target plants. It has been used to control weeds in cereal, corn, sorghum, onions, flax, mint, turf, and on non-cropland. Anomalies in rat fetuses exposed to bromoxynil suggest that it is a teratogen. Workers chronically exposed to bromoxynil over a year long span showed symptoms of weight loss, fever, vomiting, headache, and urinary problems. Bromoxynil is a Restricted Use Pesticide (RUP), not registered for homeowner use. Bromoxynil has a low persistence in soil (EXTOXNET, June 1996, Bromoxynil Pesticide Information Profile).

The left-most pathway for bromoxynil oxidation to 3-oxoadipate is based on Topp et al. (1992), who propose that bromoxynil is degraded by the same enzymes which degrade PCP. The proposed pathway for bromoxynil oxidation to 3,5-dibromo-4-hydroxybenzoate is based on Vokounova et al. (1992), McBride et al. (1986), and Stalker et al. (1988). Verhagen et al. (1998) suggest that 3,5-dibromo-4-hydroxybenzoate can be decarboxylated to 2,6-dibromophenol when incubated in methanogenic sludge. This map is also available in a graphic (9K) format.


          Bromoxynil                      Bromoxynil                      Bromoxynil
      Flavobacterium sp.             Klebsiella pneumoniae           Klebsiella pneumoniae
                                    Rhodococcus rhodochrous             subsp. ozaenae
              |                               |                               |
              |                               |                               |
              |                               | nitrile                       |
              |                               | hydratase                     |
              | pentachloro-                  |                               |
              | phenol                        |                               | bromoxynil
              | monooxygenase                 v                               | nitrolase
              |                 3,5-Dibromo-4-hydroxybenzamide                |
              |                               |                               |
              v                               |                               |
   2,6-Dibromohydroquinone<---+               |                               |
              |               |               | bromoxynil                    |
              |               |               | nitrolase                     |
              | 2,6-DiCH      |               |                               |
              | dioxygenase   |               |                               |
              |               |               |                               |
              v               |               v                               |
    [(2E,4E)-1,5-Dibromo-     | 3,5-Dibromo-4-hydroxybenzoate <---------------+
      3-hydroxy-muconic       |     methanogenic microbial
        semialdehyde]         |           consortium
              |               |               |
              | spontaneous   |               | 3,5-dibromo-
              | hydrolysis    |               | 4-hydroxybenzoate
              |               |               | decarboxylase
              v               |               v
    2-Bromomaleylacetate      |        2,6-Dibromophenol
              |               |               |
              |               |               | chlorophenol
              | maleylacetate |               | 4-monooxygenase
              | reductase     |               |
              |               +---------------+
              v
        Maleylacetate
              |
              |
              |
              v
            to the
      Pentachlorophenol
       Family Pathway

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Page Author(s): William C. Ford

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