Permethrin Pathway Map

Permethrin is a synthetic insecticide of the pyrethroid family. Pyrethroids are derived from botanical pyrethrins. Approximately 2 million pounds of permethrin are applied annually for agricultural, residential, and public health use in the United States (US EPA, 2009). Like other pyrethroid insecticides, permethrin has a higher insect to mammal ratio of toxicity than organochlorine or organophosphate insecticides (Laffin et al., 2010).

Permethrin biodegradation begins with ester hydrolysis (Maloney et al., 1988), an initial step widespread in pyrethroid metabolism, to produce 3-phenoxybenzyl alcohol and the side chain carboxylate. 3-Phenoxybenzyl alcohol is oxidized to 3-phenoxybenzoate, a major intermediate in pyrethroid insecticide metabolism. It then undergoes angular 1,6 dioxygenation by phenoxybenzoate dioxygenase. The resulting dihydrodiol spontaneously cleaves its ether to produce phenol and 3,4-dihydroxybenzoate (Halden et al., 2000). The other product of the initial esterase hydrolysis, 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate, is mineralized to CO₂, but the pathway and organisms that perform these steps are not known (Jordan et al., 1982).

The following is a text-format permethrin pathway map. Organisms that 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.

                                    Permethrin
                               Bacillus cereus SM3
                              Achromobacter sp. SM-2
     	                   Pseudomonas fluorescens SM-1
                               Klebsiella sp. ZD112
                               Sphingobium sp. JZ-2
                              Aspergillus niger ZD11
                                        |
                                        |
                                        | pyrethroid hydrolase
                                        |
                                        |
                                        v
             3-Phenoxybenzyl alcohol    +         3-(2,2-dichloroethenyl)-
                        |                   2,2-dimethylcyclopropanecarboxylate
                        |                                    |
                        | 3-phenoxybenzyl alcohol            v A
                        | dehydrogenase                      |
                        |                                    |
  from the              v                                    v
Cypermethrin->3-Phenoxybenzaldehyde                         CO2
  Pathway               |
                        |
                        | 3-phenoxybenzaldehyde
                        | dehydrogenase
                        |
                        v
                3-Phenoxybenzoate
                        |
                        |
                        | phenoxybenzoate
                        | 1,2-dioxygenase
                        |
                        v
  3,4-Dihydroxybenzoate + Phenol
            |               |
            |               |
            |               |
            |               |
            |               |
            v               v
          to the          to the
         Vanillin      Phenol Family
         Pathway         Pathway

Page Author(s): Jeffrey P. Osborne, Manchester College

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