Non-Selenium-Dependent Glutathione Peroxidase

Abstract

Recently a non-selenium-dependent glutathione peroxidase activity (non-Se GSH-Px) has been recognized in rat liver in addition to the selenium-dependent glutathione peroxidase (Se GSH-Px). Work by several groups indicates that non-Se GSH-Px is due to GSH S-transferase B and possibly GSH S-transferases A and C. Kinetic studies of GSH S-trans-ferase B reveal the Km of its non-Se GSH-Px activity with cumene hydroperoxide to be 0.55 mM and that with t-butyl hydroperoxide to be 2.3 mM. Non-Se GSH-Px will not utilize 0.25 mM H2O2 as a substrate. In contrast Se GSH-Px utilizes all these substrates and Km’s are in the range of 10–50 μM. Non-Se GSH-Px is found in rat liver, kidney, testis, adrenal, brain, and fat. It is present in liver from hamster, rat, sheep, pig, chicken, human being, and guinea pig. Because of its unfavorable Km’s when compared with Se GSH-Px, the role of non-Se GSH-Px is uncertain. However, it increases in the rat liver in selenium deficiency; and, using a hemoglobin-feee liver perfusion system, it has been shown to remove organic hydroperoxides in a selenium-deficient liver. Thus, it may function in peroxide metabolism under some conditions.