title: Epoxide formation on the aromatic B ring of flavanone by biphenyl dioxygenase of Pseudomonas pseudoalcaligenes KF707.
abstract: Prokaryotic dioxygenase is known to catalyze aromatic compounds into their corresponding cis-dihydrodiols without the formation of an epoxide intermediate. Biphenyl dioxygenase from Pseudomonas pseudoalcaligenes KF707 showed novel monooxygenase activity by converting 2(R)- and 2(S)-flavanone to their corresponding epoxides (2-(7-oxabicyclo[4.1.0]hepta-2,4-dien-2-yl)-2, 3-dihydro-4H-chromen-4-one), whereby the epoxide bond was formed between C2' and C3' on the B ring of the flavanone. The enzyme also converted 6-hydroxyflavanone and 7-hydroxyflavanone, which do not contain a hydroxyl group on the B-ring, to their corresponding epoxides. In a previous report (S.-Y. Kim, J. Jung, Y. Lim, J.-H. Ahn, S.-I. Kim, and H.-G. Hur, Antonie Leeuwenhoek 84:261-268, 2003), however, we found that the same enzyme showed dioxygenase activity toward flavone, resulting in the production of flavone cis-2',3'-dihydrodiol. Extensive structural identification of the metabolites of flavanone by using high-pressure liquid chromatography, liquid chromatography/mass spectrometry, and nuclear magnetic resonance confirmed the presence of an epoxide functional group on the metabolites. Epoxide formation as the initial activation step of aromatic compounds by oxygenases has been reported to occur only by eukaryotic monooxygenases. To the best of our knowledge, biphenyl dioxygenase from P. pseudoalcaligenes KF707 is the first prokaryotic enzyme detected that can produce an epoxide derivative on the aromatic ring structure of flavanone.
authors.affiliation: Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors.forename: Jaehong
authors.initials: J
authors.lastname: Han
authors.forename: Song-Young
authors.initials: SY
authors.lastname: Kim
authors.forename: Jihyun
authors.initials: J
authors.lastname: Jung
authors.forename: Yoongho
authors.initials: Y
authors.lastname: Lim
authors.forename: Joong-Hoon
authors.initials: JH
authors.lastname: Ahn
authors.forename: Su-Il
authors.initials: SI
authors.lastname: Kim
authors.forename: Hor-Gil
authors.initials: HG
authors.lastname: Hur
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001709:Biotechnology / Q000379:methods; D049308:Dioxygenases / Q000378:metabolism*; D004852:Epoxy Compounds / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D044950:Flavanones / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D044205:Pseudomonas pseudoalcaligenes / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004852:Epoxy Compounds; D044950:Flavanones; D011994:Recombinant Proteins; D010105:Oxygenases; D049308:Dioxygenases; C023172:toluene dioxygenase; C028610:flavanone