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Updated: Aug 18, 2026

Light-driven Enzymatic Decarboxylation
Published on: May 22, 2016
The autoxidation of the reduced forms of EO9
J Butler1, V J Spanswick, J Cummings
1CRC Department of Biophysical Chemistry, Paterson Institute for Cancer Research, Christie Hospital, Manchester, UK.
Abstract:
The properties of the semiquinone radical from [3-hydroxy-5-aziridinyl-1-methyl-2-(1H-indole-4,7-indi one)-prop-beta-en-alpha-ol], EO9, have been studied using pulse-radiolysis techniques. The reduction potential of the semiquinone of EO9 at pH7.4, E(EO9/EO9-), is -253 +/- 6 mV and hence this quinone can be readily reduced by one-electron reducing enzymes such as cytochrome P450 reductase and xanthine oxidase. However, the radical is unstable in the presence of oxygen (k = 1.3 +/- 0.15 x 10(8) M-1 s-1). The semiquinone radicals and the hydroquinone are in equilibrium although the formation of the hydroquinone is favoured t physiologically relevant pH. The hydroquinone of EO9 is also unstable in the presence of oxygen and it is predicted that in fully aerated solutions, its half life is 1.5 +/- 0.3 seconds. These results are discussed in view of the selective cytotoxicity of EO9 and its ability to undergo bioreductive activation by one-electron reducing enzymes and DT-diaphorase.
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