title: Characterization of a class alpha glutathione-S-transferase with glutathione peroxidase activity in human liver microsomes.
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.
authors.affiliation: Department of Veterinary Science and The Center for Molecular Toxicology and Carcinogenesis, 115 Henning Building, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: K Sandeep
authors.initials: KS
authors.lastname: Prabhu
authors.forename: Padala V
authors.initials: PV
authors.lastname: Reddy
authors.forename: Emily C
authors.initials: EC
authors.lastname: Jones
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Liken
authors.forename: C Channa
authors.initials: CC
authors.lastname: Reddy
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001555:Benzene Derivatives / Q000378:metabolism; D045744:Cell Line, Tumor; D004137:Dinitrochlorobenzene / Q000378:metabolism; D004285:Dogs; D005609:Free Radicals / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005979:Glutathione Peroxidase / Q000378:metabolism*; D005982:Glutathione Transferase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007527:Isoenzymes / Q000145:classification / Q000235:genetics / Q000378:metabolism; D045022:Lactate Dehydrogenases / Q000378:metabolism; D008054:Lipid Peroxides / Q000737:chemistry / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology*; D016877:Oxidants / Q000737:chemistry / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012756:Sheep; D013379:Substrate Specificity; D020298:U937 Cells
chemical_list: D000447:Aldehydes; D001555:Benzene Derivatives; D004137:Dinitrochlorobenzene; D005609:Free Radicals; D007527:Isoenzymes; D008054:Lipid Peroxides; D016877:Oxidants; D011994:Recombinant Proteins; D006861:Hydrogen Peroxide; D045022:Lactate Dehydrogenases; D005979:Glutathione Peroxidase; D005982:Glutathione Transferase; C027576:4-hydroxy-2-nonenal; C007164:cumene hydroperoxide