Glutathione peroxidase activity of glutathione-S-transferases purified from rat liver

Abstract

Gel filtration chromatography demonstrated the presence of two peaks of glutathione peroxidase activity assayed with cumene hydroperoxide in the soluble fraction of rat liver, brain, kidney, and testis. The peak with an approximate molecular weight of 45,000 (GSH-Px II) was purified from rat liver labeled in vivo with Na 2 75SeO 3. Chromatography on DEAE-cellulose, Sephadex G-150, DEAE-cellulose, and CM-cellulose resulted in the co-purification of glutathione-S-transferase activity measured with 1-chloro-2,4-dinitrobenzene and glutathione peroxidase activity assayed with cumene hydroperoxide, and in the removal of all detectable 75Se. Studies on GSH-Px II indicated that the apparent K m for both cumene and t-butyl hydroperoxides was considerably higher than that for purified seleno-glutathione peroxidase. The V max estimated with cumene hydroperoxide was only 1 300 of that determined for the selenoenzyme at pH 7.5 and with 1 mM GSH.