Abstract

Introduction

One-electron reduction of aminochrome

Two-electron reduction of aminochrome

Conclusions

References

Discussion
Board

One possible source of free radicals may involve the oxidation of dopamine to the corresponding o-quinone (aminochrome) and its activation to reactive oxyygen species (1,2. We have obtained strong evidences in vitro with pure enzymes supporting our hypothesis (1-3) that one-electron reduction of aminochrome to o-semiquinone radical is the step where reactive oxygen species are formed during the oxidative process of dopamine. Aminochrome o-semiquinone is extremely reactive (http://www.med.uchile.cl/oqclub/news3.html) and autoxidize in the presence of oxygen giving rise a redox cycling process which is accelerated by the antioxidant superoxide dismutase and catalase (1). In addition, we found that there are two antioxidant reactions which can protect the cell against the reactive oxygen species formed during dopamine oxitadion: 1) two-electron reduction of aminochrome to o-hydroquinone catalyzed by DT-diaphorase(3). DT-diaphorase compete with one-electron quinone reductases to reduce aminochrome to o-hydroquinone which can be conjugated by sulfotransferase and COMT; 2) reductive conjugation of aminochrome catalyzed by glutathione transferase M1-1 and M2-2 (4,5). This conjugate is resistent to biological oxidizing agents such as dioxygen, superoxide radicals and hydrogen peroxide. 1.Biochem. Mol . Med. 54, 12 18 (1995) 2.Biochim. Biophys. Acta 1381, 1-6 (1998) 3.Chem.-Biol. Interactions 72, 309-324, (1989) . 4.J. Biol. Chem 272, 5727-5731 (1997) 5.Biochem . J 342, 25-28 (1997)

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Presentation Number SAsegura-aguilar0402
Keywords: aminochrome, free radicals, o-quinone, neurotoxicity, neurodegeneration