Kinetic study of the reaction of glutathione peroxidase with peroxynitrite |
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Authors: | K Briviba R Kissner WH Koppenol H Sies |
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Affiliation: | Center for Craniofacial--Head and Neck Surgery, Department of Otolaryngology--Head and Neck Surgery, University of Colorado Health Sciences Center, Denver, USA. kchowdhury@uky.campus.mci.net |
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Abstract: | Glutathione peroxidases and their mimics, e.g., ebselen or diaryl tellurides, efficiently reduce peroxynitrite/peroxynitrous acid (ONOO-/ONOOH) to nitrite and protect against oxidation and nitration reactions. Here, we report the second-order rate constant for the reaction of the reduced form of glutathione peroxidase (GPx) with peroxynitrite as (8.0 +/- 0.8) x 10(6) M-1 s-1 (per GPx tetramer) at pH 7.4 and 25 degreesC. The rate constant for oxidized GPx is about 10 times lower, (0.7 +/- 0.2) x 10(6) M-1 s-1. On a selenium basis, the rate constant for reduced GPx is similar to that obtained previously for ebselen. The data support the conclusion that GPx can exhibit a biological function by acting as a peroxynitrite reductase. |
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