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Applied and Environmental Microbiology, September 2005, p. 5354-5361, Vol. 71, No. 9
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.9.5354-5361.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Epoxide Formation on the Aromatic B Ring of Flavanone by Biphenyl Dioxygenase of Pseudomonas pseudoalcaligenes KF707

Jaehong Han,¹ Song-Young Kim,^2, Jihyun Jung,³ Yoongho Lim,³ Joong-Hoon Ahn,³ Su-Il Kim,² and Hor-Gil Hur^4*

Metalloenzyme Research Group, BET Research Institute and Department of Biotechnology, Chung-Ang University, Anseong, Korea,¹ School of Agricultural Biotechnology, Seoul National University, Seoul, Korea,² Bio/Molecular Informatics Center, Konkuk University, Seoul, Korea,³ Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Korea⁴

Received 25 January 2005/ Accepted 19 April 2005

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.

Present address: Institute of Bioscience and Biotechnology, Daewoong Co., Ltd., Kyunggi-Do 449-814, Korea.