Bisphenol A Pathway Map

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This pathway was contributed by Prasad Kotharu, and completed by Lynda Ellis and Shawn Balcome, University of Minnesota.

Bisphenol A is widely used as a monomer for the production of polymers, such as epoxy resins and polycarbonate plastics. These plastics are used in many food and drink packaging applications. When the resins are inert materials, they are commonly used as lacquers to coat metal products such as food cans, bottle tops and water supply pipes. More information on this compound can be found at the Bisphenol A website from the Bisphenol A Global Industry Group and the Bisphenol A page at the Hormone Disrupting Compounds site.

Bisphenol A is metabolized by a Gram-negative aerobic bacterium (strain MV1) via a novel pathway involving oxidative skeletal rearrangement. The metabolism involves two primary pathways: a minor pathway, in which Bisphenol A is first oxidized to a triol, and a major pathway, in which Bisphenol A is metabolized to form the intermediates 4-hydroxybenzoate and 4-hydroxyacetophenone that are converted to carbon dioxide and biomass (Spivack et al., 1994).

Sphingobium xenophagium Bayram and Sphingomonas sp. strain TTNP3 can metabolize bisphenol A by an ipso-substitution mechanism that involves ring hydroxylation at the site of the substituent. This proposed hydroxylation product can be cleaved to form hydroquinone and a proposed 2-(4-hydroxyphenyl)-isopropyl cation. The cation can be transformed to 4-(2-hydroxypropan-2-yl)phenol, which can eliminate water to form 4-isopropenylphenol. 4-Isopropenylphenol can be reduced to 4-isopropylphenol. These are the reactions found in both organisms. There are other possible routes (not shown here), including formation of a 2-(4-hydroxyphenyl)-isopropyl anion instead of the cation, to the above products, and other side reactions occur in one organism or the other (Gabriel et al., 2007, Kolvenbach et al., 2007).

Sphingobium fuliginis TIK-1 can metabolize and grow on 4-isopropylphenol. S. fuliginis is proposed to hydroxylate 4-ispropylphenol to 4-isopropylcatechol, which is metabolized by a meta-cleavage pathway. 3-Methyl-2-butanone was the major degradation product observed (Toyama et al., 2010).

The following is a text-format Bisphenol A 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.

                        Graphical Map (18 K)                              |                             Graphical Map (11 K)

                             Bisphenol A <------------ from the Tetrabromobisphenol A Pathway ------------>  Bisphenol A
                  Gram- aerobic bacterium strain MV1                                                Sphingobium xenophagum Bayram
                                 |                                                                  Sphingomonas sp. strain TTNP3 
                                 |                                                                               |
                                 |                                                                               |
                   +-------------+-------------+                                                                 |
                   |                           |                                                                 |
       bisphenol A |                           | bisphenol A                                                     | bisphenol A
     hydroxylase B |                           | hydroxylase A                                                   | 1-monooxygenase
                   |                           |                                                                 |
                   v                           v                                                    +------------+-------------+
        1,2-bis(4-Hydroxyphenyl)    2,2-bis(4-Hydroxyphenyl)                                        |                          |
             -2-propanol                  1-propanol----------------------+                         |                          |
                   |                           |                          |                         |                          |
 1,2-bis(4-Hydroxy |                           |                          | 2,2-bis(4-Hydroxy-      |                          |
   -phenyl)-2-pro- |                           v A                        | phenyl)-1-propanol      |                          |
 panol dehydratase |                           |                          | hydroxylase             |                          |
                   |                           |                          |                         |                          |
                   v                           v                          v                         v                          v
          4,4'-Dihydroxy-alpha      2,2-bis(4-Hydroxyphenyl)   2,3-bis(4-Hydroxyphenyl)        Hydroquinone          [2-(4-Hydroxyphenyl)-]          
           -methylstilbene               1-propanoate              -1,2-propanediol                    |              [isopropyl cation]
                   |                                                      |                            |                       |
   4,4'-dihydroxy- |                                                      | 2,3-bis(4-hydroxyphenyl)   v                       |
 alpha-methylstil- |                                                      | -1,2-propanediol         to the                    |
  bene dioxygenase |                                                      | dioxygenase        Nitrophenol Pathway             |
                   |                                                      |                                                    v
         +---------+---------+                              +-------------+-------------+                          4-(2-Hydroxypropan-2-yl)-
         |                   |                              |                           |                                    phenol
         |                   |                              |                           |                                      |
         |                   |                              |                           |                                      | 4-(2-hydroxypropan-2-yl)-
         v                   v                              v                           v                                      | phenol dehydratase
     4-Hydroxy-          4-Hydroxy-                     4-Hydroxy-              4-Hydroxyphenacyl                              |
    benzaldehyde        acetophenone                     benzoate <----------------- alcohol                                   v      
         |                   |                              |      2,4'-dihydroxy-                                    4-iso-Propenylphenol
         |                   |                              |      acetophenone                                                |
         |                   |                              |      dioxygenase                                                 | 4-iso-Propenylphenol
         |                   |                              |                                                                  | reductase
         v                   v                              v                                                                  |
       to the              to the                         to the                                                               v
 Toluene Pathway   4-Hydroxyacetophenone             Vanillin Pathway                                                  4-iso-Propylphenol
                          Pathway                                                                                  Sphingobium fuliginis TIK-1
                                                                                                                               | 4-iso-Propylphenol
                                                                                                                               | 2-monooxygenase
                                                                                                                               v B
                                                                                                                   |                       |
                                                                                                                   |                       |
                                                                                                                   |                       |
                                                                                                                   v                       v
                                                                                                               [Pyruvate]         3-Methyl-2-butanone

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Page Author(s): Prasad Kotharu

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