Mechanisms of formation and decomposition of hypervalent chromium metabolites in the glutathione-chromium (VI) reaction.
A long-lived chromium(IV) intermediate is generated during the reaction between Cr(VI) and glutathione in glycine below pH 3. The intermediate reacts with the tripeptide to produce Cr(III) and oxidized glutathione. A dynamic magnetic susceptibility measurement based on a nuclear magnetic resonance method yielded a 2.8 microB magnetic movement for the chromium(IV) species. The intermediate is formed by parallel third-order and second-order processes. The third-order process (k = 5.9 x 10(2) M-2 s-1) involves first-order participation by each of the oxidant, reductant, and hydrogen ions. A hydrogen ion independent pathway leads to a sluggish second-order process (k = 0.11 M-1 s-1) that is first order with respect to reduced glutathione [GSH] and [Cr(VI)]. Chromium(IV) species is reduced to Cr(III) by a second-order process (k = 0.13 M-1 s-1) that is first order in each of [Cr(IV)] and [GSH] and does not depend on [H+]. At pH 3.4, a chromium(V) species was detected as a minor intermediate as well. In the pH range 6.5-7.5, three dominant chromium(V) intermediates were detected. The existence of Cr(IV) in low pH offers an opportunity to examine the mechanism of DNA damage by this rare oxidation state.
Moghaddas
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S
Department of Chemistry, Kent State University, Ohio 44240.
Gelerinter
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E
Bose
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RN
D002857:Chromium / Q000737:chemistry*; D004249:DNA Damage; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005978:Glutathione / Q000737:chemistry*; D005998:Glycine; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction
D002857:Chromium; D005978:Glutathione; D005998:Glycine