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Updated: Feb 10, 2026

Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Evidence for the Formation of a Radical-Mediated Flavin-N5 Covalent Intermediate
Yumin Dai1, Hannah Valentino1, Pablo Sobrado1
1Department of Biochemistry and Center for Drug Discovery, Virginia Tech, 360 West Campus Drive, Blacksburg, VA, 24061, USA.
Abstract:
The redox-neutral reaction catalyzed by 2-haloacrylate hydratase (2-HAH) leads to the conversion of 2-chloroacrylate to pyruvate. Previous mechanistic studies demonstrated the formation of a flavin-iminium ion as an important intermediate in the 2-HAH catalytic cycle. Time-resolved flavin absorbance studies were performed in this study, and the data showed that the enzyme is capable of stabilizing both anionic and neutral flavin semiquinone species. The presence of a radical scavenger decreases the activity in a concentration-dependent manner. These data are consistent with the flavin iminium intermediate occurring by radical recombination.
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