Thiophene-based compounds are relatively abundant in the environment. They can comprise 1-3% of crude petroleum, and they also have specialty uses as building blocks in pharmaceuticals and organic chemistry (Roncali (1992) Chem Rev 92: 711-738). Many different thiophene compounds are naturally produced in plant roots, especially in plants of the Tagetes genus (Jacobs et al., 1995). These compounds include alpha-terthienyl, which appears to be an effective pesticide against a wide variety of organisms (Nivsarkar, Cherian, and Padh (2001) Current Science 81: 667-672).
The enzymes involved in microbial degradation of thiophene-2-carboxylate (T2C) are not fully characterized. However, the pathway shown on the left below has been documented for multiple bacterial species, and Aquamicrobium defluvii NKK has been found to use it under both aerobic and anaerobic conditions (Bambauer et al., 1998; Cripps, 1973). In this pathway, T2C is ligated to CoA, oxidized, and then undergoes ring opening with the subsequent loss of sulfide. Hydrolysis releases the intermediary metabolite, 2-oxoglutarate, from the CoA. T2C-CoA thioesterase activity, which regenerates T2C from T2C-CoA, has also been detected (Bambauer et al., 1998).
A separate T2C degradation pathway (shown on the right) that does not support growth was described in a photosynthetic bacterium named strain H45-2 (Tanaka, H. et al. (1982) Agric. Biol. Chem. 46:1429-1438). Cells grown photosynthetically and anaerobically on benzoate or succinate transformed T2C to tetrahydrothiophene-2-carboxylate (major product of benzoate-grown cells) and 3-hydroxytetrahydrothiophene-2-carboxylate (major product of succinate-grown cells).
The following is a text-format thiophene-2-carboxylate 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 (11k) format.
Thiophene-2-carboxylate Thiophene-2-carboxylate Vibrio sp. YC1 strain H45-2 Rhodococcus sp. / \ Flavobacterium sp. / \ Escherichia coli K-12 A / \ B Xanthobacter tagetidis v v Aquamicrobium defluvii NKK / \ | / \ | v v | thiophene-2- Tetrahydro- 3-Hydroxytetrahydro- | carboxylate-CoA ligase thiophene- thiophene- | 2-carboxylate 2-carboxylate | v Thiophene-2-carboxyl-CoA | | | thiophene-2-carboxyl- | CoA monooxygenase | | v 5-Oxo-4,5-dihydrothiophene-2-carboxyl-CoA | | | thiolester hydrolase | | v (2Z)-5-Carboxy-2-sulfanylpent-2-enoyl-CoA | | | thiol hydrolase | | v 2-Oxoglutaryl-CoA <----- from the Furfural Pathway | | | 2-oxoglutaryl- | CoA thioesterase | | v 2-Oxoglutarate | | | | v Intermediary Metabolism (KEGG)
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