Pathways carbazole degradation

Figure 17. The proposed microbial degradation pathway for carbazole.

Some of the enzymes involved in the known pathways for the degradation of quinoline have been isolated and purified. However, not all enzymes have been identified, or characterized. In this section, we will consider the enzymes associated with the degradation of quinoline (and related compounds), carbazole and indole. To examine the enzymatic work, the reader is referred to the previous section, in which the metabolic pathways were detailed. 

Carbazole, A-methylcarbazole, IV-ethylcarbazole, dibenzofuran, dibenzothiophene, fluorene, dibenzo-p-dioxin, phenoxathiin, phenoxazine, phenothiazine, xanthene, biphenyl, naphthalene, phenanthrene, anthracene, and fluoranthene could be transformed by E. coli, [314] which was transformed using a plasmid bearing the carAa, Ac, and Ad genes, and expressing only the carA-encoded proteins. Further work is needed to develop a final biocatalyst and to prove the advantages that this degradative pathway would incorporate in a refining bioprocess. 

Whereas degradation of the carboxylates of the monocyclic furan, thiophene, and pyrrole involves hydroxylation, metabolic pathways for their benzo analogues apparently involve dioxygenation. This has been proposed for indole (Figure 6.48) (Fujioka and Wada 1968), carbazole (Sato et al. 

---