Selenium redox biochemistry of zinc–sulfur coordination sites in proteins and enzymes
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Discussion
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Implication
Biochemical analysis reveals selenium compounds catalyze zinc release from zinc-sulfur proteins like metallothionein, suggesting a key redox mechanism underlying selenium antioxidant actions.
Key Points
- To investigate whether zinc-sulfur coordination centers in proteins and enzymes serve as direct targets of selenium redox biochemistry and drive zinc release.
- Assayed the chemical reactivity of zinc-coordinated thiolates (metallothionein) and uncoordinated thiolates (glutathione) with aromatic selenium compounds across diverse oxidation states, including benzeneseleninic acid, benzeneselenenyl chloride, and selenocystamine.
- Evaluated catalytic zinc release by glutathione peroxidase in the presence of t-butyl hydroperoxide and measured reaction rates in the presence of excess competing glutathione.
- Benzeneseleninic acid and benzeneselenenyl chloride reacted rapidly with metallothionein in substoichiometric and 1:1 molar stoichiometries, respectively, mobilizing bound zinc.
- Glutathione peroxidase catalyzed the oxidation of metallothionein and accelerated zinc release during hydroperoxide reduction.
- Zinc mobilization was only partially suppressed in the presence of excess glutathione, supporting the likelihood that zinc-thiolate coordination centers serve as physiological targets for selenium in vivo.
Cite This Study
Jacob et al. (1999) studied this question.