Nitrofen Pathway Map

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This pathway was contributed by Sujana Mittapalli, University of Minnesota, BioC/MicE 5309.

Nitrofen is a potent herbicide and has the ability to induce various physiological effects, including master cell activation, organ morphogenesis and severe endocrine disruptor activities. Nitrofen, in its purest form is a colorless and crystalline solid. The technical material is a brown, free flowing solid with a slight aromatic odor. The melting point of the technical material is 64-71C and the density is 1.80g/cm3 at 83C. It is used as a pre or post-emergence contact herbicide. Moderate application rates give selective control in cereals, certain ornamentals, vegetable crops, sugar beet and paddy fields. High application rates will give total vegetation control. Nitrofen requires adequate moisture for full effectiveness.

Sphingomonas wittichii RW1 is a very potent diphenyl ether herbicide metabolizing bacterium with broad substrate specificity (Keum et al., 2008). The interesting aspect of the Nitrofen degradation by this strain is the initial reduction of nitro group followed by N-acetylation. As in other Sphingomonads, dissociation of the diaryl ether bond is also found in strain RW1 during Nitrofen metabolism. Although, ether bond clevage is a common metabolic pathway of diaryl ethers in animal, plant, fungi and bacteria, corresponding enzymes of eukaryotes and prokaryotes are different. Bacterial degradation of diphenyl ethers and related environmental contaminants are usually catalyzed by multi-component dioxygenase system, while eukaryotic biodegradation is catalyzed by monooxygenase or peroxidase

(Hiratsuka et al., 2001) identified the degradation of diphenyl ether herbicides by the lignin-degrading basidomycete Coriolus versicolor. White-rot basidiomycetous fungi are capable of degrading a variety of environmentally persistent aromatic pollutants. The first metabolites of nitrofen degradation by C.versicolor are identified as p-Nitrophenol and 2,4-Dichlorophenol.

The following is a text-format nitrofen 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 (11k) format.

         Nitrofen                                  Nitrofen
  Sphingomonas wittichii                      Coriolus versicolor
            RW1                                        |
             |                                         | nitrofen
             |                                         | 1,2-dioxygenase
             | nitrofen                                |
             | nitroreductase                          +---------------------------+
             |                                         |                           |
             v                                         |                           |
       Aminonitrofen                                   v                           v
             |                                   p-Nitrophenol             2,4-Dichlorophenol
             |                                         |                           |
             | aminonitrofen                           |                           |
             | N-acetyltransferase                     |                           |
             |                                         |                           |
             v                                         v                           v
   N-acetylaminonitrofen                            to the                      to the
             |                                Nitrophenol Family       2,4-Dichlorophenoxyacetate
             | N-acetylaminonitrofen                Pathway                     Pathway
             | 1,2-dioxygenase
             |                            |
             |                            |
             |                            |
             v                            v
     2,4-Dichlorophenol           p-Acetamidophenol
             |                            |
             |                            |
             |                            | p-Acetamidophenol
             |                            | amidohydrolase
             |                            +------------------------+
             |                            |                        |
             |                            |                        |
             v                            v                        v
          to the                    p-Aminophenol               Acetate
 2,4-Dichlorophenoxyacetate               |                        |
          Pathway                         |                        |
                                          |                        |
                                          v                        v
                                       to the                 Intermediary
                                      Parathion                Metabolism
                                       Pathway                   (KEGG)

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Page Author(s): Sujana Mittapalli

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