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  • Title: Characterization of a class alpha glutathione-S-transferase with glutathione peroxidase activity in human liver microsomes.
    Author: Prabhu KS, Reddy PV, Jones EC, Liken AD, Reddy CC.
    Journal: Arch Biochem Biophys; 2004 Apr 01; 424(1):72-80. PubMed ID: 15019838.
    Abstract:
    A 25.5kDa class alpha glutathione S-transferase (GST) designated as microsomal Ya-GST or M-GSTA has been purified to electrophoretic homogeneity from human liver microsomes. Limited proteolysis, gel filtration chromatography followed by EDTA, and alkaline Na(2)CO(3) treatments of microsomes indicate that the M-GSTA is intrinsic to the microsomes. Western immunoblot analysis revealed that human liver M-GSTA and the previously reported 17-kDa microsomal GST (FEBS Lett. 315 (1993) 77) did not have immunological cross reactivity. The enzyme showed conjugation activity towards substrates like 1-chloro-2,4-nitrobenzene (CDNB) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, and 4-hydroxy-2-nonenal (4-HNE), a genotoxic alpha,beta-unsaturated aldehyde product of lipid peroxidation. In addition, the M-GSTA exhibited significant glutathione peroxidase activity towards physiologically relevant fatty acid hydroperoxides as well as phosphatidylcholine hydroperoxide, but not with H(2)O(2). C-terminal amino acid sequence analysis revealed a high homology with the human liver cytosolic GST-A1 and A3 isozymes. Western immunoblot analyses of the microsomes prepared from human hepatoblastoma (HepG2) showed that the expression of this M-GSTA was induced upon treatment with such prooxidants as H(2)O(2), suggesting that it may play an important role in the protection of cellular membranes from peroxidative damage.
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