Dibenzothiophene Degradation Pathway

Dibenzothiophene (DBT) is representative of a group of sulfur-containing heterocyclic organic compounds. Mormile and Atlas (1988) examined the degradation of 3-hydroxy-2-formylbenzothiophene and reported release of CO₂ from the ring structure of DBT under aerobic conditions. This study suggests that a succession of microbial organisms is neccesary to degrade 3-hydroxy-2-formylbenzothiophene further.

Pseudomonas sp. C18 can metabolize dibenzothiophene, naphthalene and phenanthrene by a single pathway (Denome et al., 1993). The names of the enzymes in the pathway are not given, only the DOX operon which encodes them in its 9 open reading frames (ABDEFGHIJ). The pathway is very similar to the one of naphthalene and the enzymes have high sequence identity with the naphthalene enzymes, thus the corresponding names have been used for the enzymes. Naphthalene dioxygenase, the enzyme which initiates this pathway, is used in a biotechnological process to synthesize the blue jean dye indigo. This versatile enzyme has many other catalytic abilities, which are documented in a table of the Reactions of Naphthalene 1,2-Dioxygenase.

This pathway can be contrasted to the Dibenzothiophene Desulfurization Pathway, which retains the full fuel value of the compound while eliminating the sulfur.

The following is a text-format dibenzothiophene degradation pathway map. An organism which can initiate the pathway is 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 (13k) format.

 
              Dibenzothiophene
             Pseudomonas putida                 
                     |
                     |
                     | naphthalene                     
                     | 1,2-dioxygenase                 
                     | 
                     |
                     v                               
           cis-1,2-Dihydroxy-1,2-  
           dihydrodibenzothiophene
                     |  
                     |
                     | 1,2-dihydroxy-1,2-dihydronaphthalene
                     | dehydrogenase
                     |
                     |
                     v                               
       1,2-Dihydroxydibenzothiophene                     
                     |      
                     |
                     | 1,2-dihydroxynaphthalene                    
                     | dioxygenase
                     |
                     |
                     v                               
   cis-4-[2-(3-Hydroxy)-thionaphthenyl]-      
             2-oxo-3-butenoate
                     |      
                     |
                     | 2-hydroxychromene-
                     | 2-carobxylate isomerase
                     |
                     |
                     v                               
  trans-4-[2-(3-Hydroxy)-thionaphthenyl]-     
             2-oxo-3-butenoate
                     |      
                     |
                     | trans-o-hydroxybenzylidene-
                     | pyruvate hydratase-aldolase
                     |
                     |
                     v                               
3-Hydroxy-2-formylbenzothiophene + Pyruvate    
          |                           |
          | A                         |
          v                           | 
          |                           |
          v                           v
   Carbon dioxide               Intermediary
                                 Metabolism
                                   (KEGG)

Page Author(s): Gulin Oz and Dong Jun Oh

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