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Ebselen: a thioredoxin reductase-dependent catalyst for alpha-tocopherol quinone reduction.
Jianguo Fang1, Liangwei Zhong, Rong Zhao
1The Medical Nobel Institute for Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Toxicology and Applied Pharmacology
|June 28, 2005
Summary
Ebselen, a drug, can reduce alpha-tocopherol quinone (TQ) to a potent antioxidant via the thioredoxin system. This novel mechanism explains ebselen's antioxidant effects in vivo.
Area of Science:
- Biochemistry
- Redox Biology
- Pharmacology
Background:
- The thioredoxin system (thioredoxin, thioredoxin reductase, NADPH) is crucial for reducing protein disulfides.
- Ebselen, a selenazole drug, is known to interact with the thioredoxin system.
- Alpha-tocopherol quinone (TQ) is an oxidation product of alpha-tocopherol and lacks antioxidant activity.
Purpose of the Study:
- To investigate if ebselen can reduce TQ in the presence of the thioredoxin system.
- To elucidate the mechanism by which ebselen facilitates TQ reduction.
- To understand the role of this interaction in ebselen's antioxidant function.
Main Methods:
- Enzymatic assays were used to test the reduction of TQ by ebselen.
- The involvement of thioredoxin reductase (TrxR) was investigated.
- The generation of ebselen selenol as a reactive intermediate was studied.
Main Results:
- TQ is not a direct substrate for TrxR.
- Ebselen effectively catalyzes the reduction of TQ in the presence of TrxR.
- This reduction occurs via ebselen selenol, formed by rapid ebselen reduction by TrxR.
- The product, alpha-tocopherolhydroquinone (TQH(2)), is a potent antioxidant.
Conclusions:
- Ebselen acts as a mediator to reduce TQ via the thioredoxin system.
- This pathway generates the antioxidant TQH(2) from TQ.
- This novel mechanism provides insight into ebselen's antioxidant properties in biological systems.