title: Characterization of an intradiol dioxygenase involved in the biodegradation of the chlorophenoxy herbicides 2,4-D and 2,4,5-T.
abstract: Hydroxyquinol 1,2-dioxygenase, an intradiol dioxygenase, which catalyzes the cleaving of the aromatic ring of hydroxyquinol, a key intermediate of 2,4-D and 2,4,5-T degradation, was purified from Nocardioides simplex 3E cells grown on 2,4-D as the sole carbon source. This enzyme exhibits a highly restricted substrate specificity and is able to cleave hydroxyquinol (K(m) for hydroxyquinol as a substrate was 1.2 microM, V(max) 55 U/mg, K(cat) 57 s-1 and K(cat)/K(m) 47.5 microM s-1), 6-chloro- and 5-chlorohydroxyquinol. Different substituted catechols and hydroquinones are not substrates for this enzyme. This enzyme appears to be a dimer with two identical 37-kDa subunits. Protein and iron analyses indicate an iron stoichiometry of 1 iron/65 kDa homodimer, alpha2 Fe. Both the electronic absorption spectrum which shows a broad absorption band with a maximum at 450 nm and the electron paramagnetic resonance spectra are consistent with a high-spin iron(III) ion in a rhombic environment typical of the active site of intradiol cleaving enzymes.
authors.affiliation: Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow Region.
authors.forename: V M
authors.initials: VM
authors.lastname: Travkin
authors.forename: A P
authors.initials: AP
authors.lastname: Jadan
authors.forename: F
authors.initials: F
authors.lastname: Briganti
authors.forename: A
authors.initials: A
authors.lastname: Scozzafava
authors.forename: L A
authors.initials: LA
authors.lastname: Golovleva
mesh_terms: D015085:2,4,5-Trichlorophenoxyacetic Acid / Q000378:metabolism*; D015084:2,4-Dichlorophenoxyacetic Acid / Q000378:metabolism*; D000192:Actinomycetales / Q000201:enzymology*; D001673:Biodegradation, Environmental; D002396:Catechols / Q000378:metabolism; D049308:Dioxygenases; D004578:Electron Spin Resonance Spectroscopy; D006540:Herbicides / Q000378:metabolism*; D006873:Hydroquinones / Q000378:metabolism; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D013379:Substrate Specificity
chemical_list: D002396:Catechols; D006540:Herbicides; D006873:Hydroquinones; D015084:2,4-Dichlorophenoxyacetic Acid; D015085:2,4,5-Trichlorophenoxyacetic Acid; D010105:Oxygenases; D049308:Dioxygenases; C041894:hydroxyquinol 1,2-dioxygenase