Anaerobic toluene-catabolic pathway in denitrifying Thauera aromatica: activation and β-oxidation of the first intermediate, (R)-(+)-benzylsuccinate
| Autor: | Johann Heider, Christina Leutwein |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Thauera
Reaction mechanism biology Thauera aromatica Stereochemistry organic chemicals Molecular Conformation Succinates Metabolic intermediate biology.organism_classification Benzoates Microbiology Toluene Cofactor Culture Media chemistry.chemical_compound Metabolic pathway chemistry Transferases Benzylsuccinate synthase biology.protein Anaerobiosis Oxidation-Reduction Methyl group |
| Zdroj: | Microbiology. 145:3265-3271 |
| ISSN: | 1465-2080 1350-0872 |
| DOI: | 10.1099/00221287-145-11-3265 |
| Popis: | Anaerobic catabolism of toluene is initiated by addition of the methyl group of toluene to the double bond of a fumarate cosubstrate to yield the first intermediate, benzylsuccinate. This reaction is catalysed by the glycyl-radical enzyme benzylsuccinate synthase, as shown for the denitrifying bacterium Thauera aromatica. Benzylsuccinate is further oxidized to benzoyl-CoA, the central intermediate of anaerobic degradation of aromatic compounds. The authors show here by experiments with cell extracts of toluene-grown T. aromatica that the pathway of benzylsuccinate oxidation requires activation of the free acid to a CoA-thioester, catalysed by a toluene-induced, reversible succinyl-CoA-dependent CoA-transferase. The product of the CoA-transferase reaction, benzylsuccinyl-CoA, is oxidized to benzoyl-CoA and succinyl-CoA in extracts of toluene-grown cells, adding proof to the proposed anaerobic toluene-catabolic pathway. The stereochemical preferences of the enzymes catalysing formation and activation of benzylsuccinate have been analysed. Benzylsuccinate synthase was found to produce exclusively (R)-(+)-benzylsuccinate, although the proposed reaction mechanism of this enzyme proceeds via radical intermediates. In accordance, the reaction of succinyl-CoA:benzylsuccinate CoA-transferase is also specific for (R)-(+)-benzylsuccinate and does not proceed with the (S)-(-)-enantiomer. |
| Databáze: | OpenAIRE |
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