title: Metabolism of chlorobiphenyls by a variant biphenyl dioxygenase exhibiting enhanced activity toward dibenzofuran.
abstract: The biphenyl dioxygenase of Burkholderia xenovorans LB400 (BphAE(LB400)) catalyzes the dihydroxylation of biphenyl and of several polychlorinated biphenyls (PCBs) but it poorly oxidizes dibenzofuran. In this work we showed that BphAE(RR41), a variant which was previously found to metabolize dibenzofuran more efficiently than its parent BphAE(LB400), metabolized a broader range of PCBs than BphAE(LB400). Hence, BphAE(RR41) was able to metabolize 2,6,2',6'-, 3,4,3',5'- and 2,4,3',4'-tetrachlorobiphenyl that BphAE(LB400) is unable to metabolize. BphAE(RR41) was obtained by changing Thr335Phe336Asn338Ile341Leu409 of BphAE(LB400) to Ala335Met336Gln338Val341Phe409. Site-directed mutagenesis was used to create combinations of each substitution, in order to assess their individual contributions. Data show that the same Asn338Glu/Leu409Phe substitution that enhanced the ability to metabolize dibenzofuran resulted in a broadening of the PCB substrates range of the enzyme. The role of these substitutions on regiospecificities toward selected PCBs is also discussed.
authors.affiliation: Institut National de la Recherche Scientifique, INRS-Institut Armand-Frappier, Laval, Québec, Canada H4K 1C2.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Viger
authors.forename: Mahmood
authors.initials: M
authors.lastname: Mohammadi
authors.forename: Diane
authors.initials: D
authors.lastname: Barriault
authors.forename: Michel
authors.initials: M
authors.lastname: Sylvestre
mesh_terms: D001572:Benzofurans / Q000737:chemistry / Q000378:metabolism*; D001713:Biphenyl Compounds / Q000737:chemistry / Q000378:metabolism*; D019117:Burkholderia / Q000201:enzymology* / Q000235:genetics; D002384:Catalysis; D049308:Dioxygenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D011078:Polychlorinated Biphenyls / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001572:Benzofurans; D001713:Biphenyl Compounds; D049308:Dioxygenases; D011078:Polychlorinated Biphenyls; D011994:Recombinant Proteins; C010574:biphenyl; C023614:dibenzofuran