title: Anaerobic metabolism of catechol by the denitrifying bacterium Thauera aromatica--a result of promiscuous enzymes and regulators?
abstract: The anaerobic metabolism of catechol (1,2-dihydroxybenzene) was studied in the betaproteobacterium Thauera aromatica that was grown with CO2 as a cosubstrate and nitrate as an electron acceptor. Based on different lines of evidence and on our knowledge of enzymes and genes involved in the anaerobic metabolism of other aromatic substrates, the following pathway is proposed. Catechol is converted to catechylphosphate by phenylphosphate synthase, which is followed by carboxylation by phenylphosphate carboxylase at the para position to the phosphorylated phenolic hydroxyl group. The product, protocatechuate (3,4-dihydroxybenzoate), is converted to its coenzyme A (CoA) thioester by 3-hydroxybenzoate-CoA ligase. Protocatechuyl-CoA is reductively dehydroxylated to 3-hydroxybenzoyl-CoA, possibly by 4-hydroxybenzoyl-CoA reductase. 3-Hydroxybenzoyl-CoA is further metabolized by reduction of the aromatic ring catalyzed by an ATP-driven benzoyl-CoA reductase. Hence, the promiscuity of several enzymes and regulatory proteins may be sufficient to create the catechol pathway that is made up of elements of phenol, 3-hydroxybenzoate, 4-hydroxybenzoate, and benzoate metabolism.
authors.affiliation: Mikrobiologie, Fakultät für Biologie, Schänzlestr. 1, D-79104 Freiburg, Germany.
authors.forename: Bin
authors.initials: B
authors.lastname: Ding
authors.forename: Sirko
authors.initials: S
authors.lastname: Schmeling
authors.forename: Georg
authors.initials: G
authors.lastname: Fuchs
mesh_terms: D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001565:Benzoates / Q000737:chemistry / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D019755:Carbon-Carbon Lyases / Q000235:genetics / Q000378:metabolism*; D002396:Catechols / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D062385:Hydroxybenzoates / Q000737:chemistry / Q000378:metabolism; D015151:Immunoblotting; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism; D010755:Organophosphates / Q000737:chemistry / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D010226:Parabens / Q000737:chemistry / Q000378:metabolism; D019800:Phenol / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D020628:Thauera / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001565:Benzoates; D002396:Catechols; D062385:Hydroxybenzoates; D009566:Nitrates; D010755:Organophosphates; D010226:Parabens; D002245:Carbon Dioxide; C032948:3-hydroxybenzoic acid; D019800:Phenol; C009091:protocatechuic acid; C074782:phenylphosphate; D044925:Oxidoreductases Acting on CH-CH Group Donors; C109030:benzoyl-coenzyme A reductase (dearomatizing); C060482:benzoyl-coenzyme A-4-oxidoreductase; D019755:Carbon-Carbon Lyases; C488635:phenylphosphate carboxylase, Thauera aromatica; C411162:3-hydroxybenzoate coenzyme A ligase; C058481:4-hydroxybenzoate coenzyme A ligase; D003066:Coenzyme A Ligases; C038193:4-hydroxybenzoic acid; C034221:catechol