Substrate specificities and electron paramagnetic resonance properties of benzylsuccinate synthases in anaerobic toluene and m-xylene metabolism
| Autor: | Christina Leutwein, Susanne Zorn, Knut Verfürth, Johann Heider, Antonio J. Pierik |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Thauera
Thauera aromatica Stereochemistry Azoarcus Xylenes Biochemistry Microbiology Substrate Specificity chemistry.chemical_compound Cresols Genetics Organic chemistry Anaerobiosis Carbon-Carbon Lyases Molecular Biology biology Xylene Electron Spin Resonance Spectroscopy Substrate (chemistry) Succinates General Medicine biology.organism_classification Toluene Biodegradation Environmental chemistry Benzylsuccinate synthase biology.protein Methyl group |
| Zdroj: | Archives of microbiology. 181(2) |
| ISSN: | 0302-8933 |
| Popis: | The anaerobic degradation pathways of toluene and m-xylene are initiated by addition of a fumarate cosubstrate to the methyl group of the hydrocarbon, yielding (R)-benzylsuccinate and (3-methylbenzyl)succinate, respectively, as first intermediates. These reactions are catalyzed by a novel glycyl-radical enzyme, (R)-benzylsuccinate synthase. Substrate specificities of benzylsuccinate synthases were analyzed in Azoarcus sp. strain T and Thauera aromatica strain K172. The enzyme of Azoarcus sp. strain T converts toluene, but also all xylene and cresol isomers, to the corresponding succinate adducts, whereas the enzyme of T. aromatica is active with toluene and all cresols, but not with any xylene isomer. This corresponds to the capabilities of Azoarcus sp. strain T to grow on either toluene or m-xylene, and of T. aromatica to grow on toluene as sole hydrocarbon substrate. Thus, differences in the substrate spectra of the respective benzylsuccinate synthases of the two strains contribute to utilization of different aromatic hydrocarbons, although growth on different substrates also depends on additional determinants. We also provide direct evidence by electron paramagnetic resonance (EPR) spectroscopy that glycyl radical enzymes corresponding to substrate-induced benzylsuccinate synthases are specifically detectable in anoxically prepared extracts of toluene- or m-xylene-grown cells. The presence of the EPR signals and the determined amount of the radical are consistent with the respective benzylsuccinate synthase activities. The properties of the EPR signals are highly similar to those of the prototype glycyl radical enzyme pyruvate formate lyase, but differ slightly from previously reported parameters for partially purified benzylsuccinate synthase. |
| Databáze: | OpenAIRE |
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