title: Enzymes of the benzoyl-coenzyme A degradation pathway in the hyperthermophilic archaeon Ferroglobus placidus.
abstract: The Fe(III)-respiring Ferroglobus placidus is the only known archaeon and hyperthermophile for which a complete degradation of aromatic substrates to CO2 has been reported. Recent genome and transcriptome analyses proposed a benzoyl-coenzyme A (CoA) degradation pathway similar to that found in the phototrophic Rhodopseudomonas palustris, which involves a cyclohex-1-ene-1-carboxyl-CoA (1-enoyl-CoA) forming, ATP-dependent key enzyme benzoyl-CoA reductase (BCR). In this work, we demonstrate, by first in vitro studies, that benzoyl-CoA is ATP-dependently reduced by two electrons to cyclohexa-1,5-dienoyl-CoA (1,5-dienoyl-CoA), which is further degraded by hydration to 6-hydroxycyclohex-1-ene-1-carboxyl-CoA (6-OH-1-enoyl-CoA); upon addition of NAD(+) , the latter was subsequently converted to β-oxidation intermediates. The four candidate genes of BCR were heterologously expressed, and the enriched, oxygen-sensitive enzyme catalysed the two-electron reduction of benzoyl-CoA to 1,5-dienoyl-CoA. A gene previously assigned to a 2,3-didehydropimeloyl-CoA hydratase was heterologously expressed and shown to act as a typical 1,5-dienoyl-CoA hydratase that does not accept 1-enoyl-CoA. A gene previously assigned to a 1-enoyl-CoA hydratase was heterologously expressed and identified to code for a bifunctional crotonase/3-OH-butyryl-CoA dehydrogenase. In summary, the results consistently provide biochemical evidence that F. placidus and probably other archaea predominantly degrade aromatics via the Thauera/Azoarcus type and not or only to a minor extent via the predicted R. palustris-type benzoyl-CoA degradation pathway.
authors: Microbiology, Faculty of Biology, University of Freiburg, Schänzlestr. 1, Freiburg, 79104, Germany.
authors: Georg
authors: G
authors: Schmid
authors: Microbiology, Faculty of Biology, University of Freiburg, Schänzlestr. 1, Freiburg, 79104, Germany.
authors: Sandra Bosch
authors: SB
authors: René
authors: Microbiology, Faculty of Biology, University of Freiburg, Schänzlestr. 1, Freiburg, 79104, Germany.
authors: Matthias
authors: M
authors: Boll
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D000693:Anaerobiosis; D019608:Archaeoglobales / Q000201:enzymology* / Q000235:genetics; D003065:Coenzyme A / Q000378:metabolism; D004746:Enoyl-CoA Hydratase / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D006836:Hydro-Lyases / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000502:physiology*; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism; D020628:Thauera / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D005290:Ferric Compounds; C037817:benzoyl-coenzyme A; D044925:Oxidoreductases Acting on CH-CH Group Donors; C109030:benzoyl-coenzyme A reductase (dearomatizing); D006836:Hydro-Lyases; C114397:cyclohexa-1,5-diene-1-carboxyl-CoA hydratase; D004746:Enoyl-CoA Hydratase; D003065:Coenzyme A