gamma-Hexachlorocyclohexane Pathway Map

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This pathway was contributed by Jiri Damborsky (Masaryk University), Yuji Nagata (University of Tokyo) and Thanh Trinh (University of Minnesota), and updated by Jenny Kang (University of Minnesota).

g-Hexachlorocyclohexane (g-HCH, BHC, lindane) is a halogenated organic insecticide that has been used worldwide for agriculture and public health. Because of its high toxicity and persistence in soil, the use of g-HCH has been prohibited in many countries. g-HCH is degraded rapidly under anaerobic conditions, but is considered extremely persistent in upland soil. Sphingomonas (formerly Pseudomonas) paucimobilis SS86 was isolated from an upland experimental field to which g-HCH was applied once a year for twelve years. The mutant of the strain SS86, named UT26, has nalidixic acid resistance as a genetic marker and utilizes g-HCH as a sole source of carbon and energy under aerobic conditions. The genes and enzymes involved in the g-HCH degradation pathway of S. paucimobilis UT26 have been investigated (Imai et al., 1991; Nagata et al., 1999, J. Ind. Microbiol. Biotechnol. 23: 380-390).

The cyanobacteria Anabeana sp. PCC7120 and Nostoc ellipsosporum have also been shown to metabolize lindane. A mixture of 1,2,4- and 1,2,3-trichlorobenzenes is produced (Kuritz and Wolk, 1995).

The absolute configuration of 2,4,5-Trichloro-2,5-cyclohexadiene-1-ol and 2,5-Dichloro-2,5-cyclohexadiene-1,4-diol have not yet been determined. The biodegradation pathway for beta-hexachlorocyclohexane is found elsewhere.

The following is a text-format gamma-Hexachlorocyclohexane 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 (18K) format.

     gamma-Hexachlorocyclohexane (g-HCH)
        Sphingomonas paucimobilis UT26
           Anabaena sp. PCC7120
           Nostoc ellipsosporum
                     |
                     |                              1,2,3-Trichlorobenzene         
                     | g-HCH dehydrochlorinase                ^
                     |                                        |
                     |                                        | C
                     v             Anabaena sp. PCC7120       ^
          1,3(R),4(S),5(S),6(R)-   Nostoc ellipsosporum       |
          Pentachlorocyclohexene -----------------------------+
                 (g-PCCH)                                     |
                     |                                        |
                     |                                        v D
                     | g-HCH dehydrochlorinase                |
                     |                                        |
                     |                                        |
                     v                       A                v
          1,3(R),4,6(R)-Tetrachloro-1,4-  ------>   1,2,4-Trichlorobenzene
            cyclohexadiene (1,4-TCDN)                    (1,2,4-TCB)
                     |                                        |
                     |                                        |
                     | haloalkane dehalogenase                v
                     |                             to the 1,2,4-TCB Pathway
                     |
                     v                       B
           2,4,5-Trichloro-2,5-           ------>     2,5-Dichlorophenol 
     cyclohexadiene-1-ol (2,4,5-DNOL)                     (2,5-DCP)
                     |
                     |
                     | haloalkane dehalogenase
                     |
                     |
                     v
      2,5-Dichloro-2,5-cyclohexadiene
            -1,4-diol (2,5-DDOL)
                     |
                     |
                     | 2,5-DDOL dehydrogenase 
                     |
                     |
                     v
         2,5-Dichlorohydroquinone      ------>     to the 2,4,5-T Pathway
                (2,5-DCHQ)
                     |
                     |
                     | 2,5-DCHQ reductive dehalogenase
                     |
                     |
                     v
           Chlorohydroquinone (CHQ)
                     |
                     |
                     | 2,5-DCHQ reductive dehalogenase
                     |
                     |
                     v
             Hydroquinone (HQ) 
                     |
                     |
                     |
                     |
                     |
                     v
                  to the
           4-Nitrophenol Pathway
        

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Page Author(s): Jiri Damborsky, Yuji Nagata, Thanh Trinh, and Jenny Kang

June 30, 2014 Contact Us

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