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Biochemistry. 2008 Aug 19;47(33):8485-90. doi: 10.1021/bi801039d. Epub 2008 Jul 25.

Detection of a C4a-hydroperoxyflavin intermediate in the reaction of a flavoprotein oxidase.

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Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Henri-Dunant Road, Patumwan, Bangkok 10300, Thailand.


This work describes for the first time the identification of a reaction intermediate, C4a-hydroperoxyflavin, during the oxidative half-reaction of a flavoprotein oxidase, pyranose 2-oxidase (P2O) from Trametes multicolor, by using rapid kinetics. The reduced P2O reacted with oxygen with a forward rate constant of 5.8 x 10 (4) M (-1) s (-1) and a reverse rate constant of 2 s (-1), resulting in the formation of a C4a-hydroperoxyflavin intermediate which decayed with a rate constant of 18 s (-1). The absorption spectrum of the intermediate resembled the spectra of flavin-dependent monooxygenases. A hydrophobic cavity formed at the re side of the flavin ring in the closed state structure of P2O may help in stabilizing the intermediate.

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