title: Hydroperoxide reduction by thioredoxin-specific glutathione peroxidase isoenzymes of Arabidopsis thaliana.
abstract: Arabidopsis thaliana contains eight glutathione peroxidase (GPX) homologs (AtGPX1-8). Four mature GPX isoenzymes with different subcellular distributions, AtGPX1, -2, -5 and -6, were overexpressed in Escherichia coli and characterized. Interestingly, these recombinant proteins were able to reduce H2O2, cumene hydroperoxide, phosphatidylcholine and linoleic acid hydroperoxides using thioredoxin but not glutathione or NADPH as an electron donor. The reduction activities of the recombinant proteins with H2O2 were 2-7 times higher than those with cumene hydroperoxide. Km values for thioredoxin and H2O2 were 2.2-4.0 and 14.0-25.4 microM, respectively. These finding suggest that GPX isoenzymes may function to detoxify H2O2 and organic hydroperoxides using thioredoxin in vivo and may also be involved in regulation of the cellular redox homeostasis by maintaining the thiol/disulfide or NADPH/NADP balance.
authors.affiliation: Department of Applied Biological Chemistry, Osaka Prefecture University, Sakai, Japan.
authors.forename: Aqib
authors.initials: A
authors.lastname: Iqbal
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Yabuta
authors.forename: Toru
authors.initials: T
authors.lastname: Takeda
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nakano
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D011994:Recombinant Proteins; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase