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Occupation of the electrophilic substrate‐binding site of glutathione S‐transferase M1‐1 enhances its function as an activator of 1‐cysteine peroxiredoxin
Author(s) -
Ralat-Touset Luis Abel,
Feinstein Sheldon I.,
Fisher Aron B.
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.556.2
Subject(s) - glutathione , chemistry , peroxidase , cysteine , peroxiredoxin , biochemistry , sulfenic acid , glutathione reductase , isozyme , substrate (aquarium) , stereochemistry , enzyme , glutathione peroxidase , biology , ecology
Glutathione S‐transferase mu (GST‐mu) can form an in vitro heterodimer with 1‐cysteine peroxiredoxin, peroxiredoxin 6 (Prdx6), in the presence of glutathione (GSH), but the peroxidase specific activity of this complex is only 1.0 μmol/min/mg Prdx6, which is ~20% of that of the complex between the pi isozyme of GST and Prdx6 under the same conditions [L.A. Ralat, Y. Manevich, A.B. Fisher, R.F. Colman, Biochemistry 45 (2006) 360–372]. These results suggested that the interactions are different between Prdx6 and GST isozymes, which share an identity of less than 30%. Here, we show that Prdx6 can reduce hydrogen peroxide at 4.7 ± 0.3 μmol/min/mg Prdx6, as assayed using the GSH reductase/GSH/NADPH‐coupled GSH‐peroxidase method, after a 1‐hour incubation with a 1:1 molar ratio of GST‐mu at pH 8, containing saturating amounts of GSH and an electrophilic GST substrate analog, 2,4‐dinitrophenol. Interestingly, after this same incubation, GST‐mu lost all of its activity with respect to monobromobimane, a substrate that occupies a distinguishable site from 2,4‐dinitrophenol. These results suggest that occupation of the electrophilic site of GST‐mu may render a conformational change which optimizes its interaction with Prdx6, allowing the transfer of GSH to the inactive Cys‐47−sulfenic acid form of Prdx6, regenerating an active Prdx6, while inhibiting GST‐mu activity. Supported by NIH/NHLBI R01554495.