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Biochem Biophys Res Commun. 2004 Dec 24;325(4):1418-23.

The unusual redox properties of flavocytochrome P450 BM3 flavodoxin domain.

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  • 1School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK.


Flavocytochrome P450 BM3 FMN domain is unique among the family of flavodoxins and homologues, in not forming a stable neutral blue FMN semiquinone radical. Anaerobic, one-electron reduction of the isolated domain over the pH 7-9.5 range showed that it forms an anionic red semiquinone that disproportionates slowly (0.014s(-1) at pH 7). The rate of disproportionation decreased at higher pH, indicating that protonation of the anionic semiquinone is an important feature of the mechanism. The reduction potential for the oxidised-semiquinone couple was determined to be -240mV and was largely independent of pH. The semiquinone appears, therefore, to be kinetically trapped by a slow protonation event, enabling it to act as a low-potential electron donor to the P450 heme.

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