TAILIEUCHUNG - Báo cáo khoa học: Hydroperoxide reduction by thioredoxin-specific glutathione peroxidase isoenzymes of Arabidopsis thaliana

Arabidopsis thalianacontains eight glutathione peroxidase (GPX) homologs (AtGPX1–8). Four mature GPX isoenzymes with different subcellular dis-tributions, 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. | ỊFEBS Journal Hydroperoxide reduction by thioredoxin-specific glutathione peroxidase isoenzymes of Arabidopsis thaliana Aqib Iqbal1 Yukinori Yabuta2 Toru Takeda2 Yoshihisa Nakano1 and Shigeru Shigeoka2 1 Department of Applied BiologicalChemistry Osaka Prefecture University Sakai Japan 2 Department of Advanced Bioscience Kinki University Nara Japan Keywords Arabidopsis glutathione peroxidase hydroperoxide thioredoxin Correspondence T. Takeda Department of Advanced Bioscience Faculty of Agriculture Kinki University 3327-204 Nakamachi Nara 631-8505 Japan Fax 81 742 43 8976 Tel 81 742 43 8179 E-mail t_takeda@ Received 22 August 2006 revised 18 October 2006 accepted 20 October 2006 doi 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 and pM 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. The generation of reactive oxygen species ROS is an inevitable process in living organisms and poses a hazard when present in high concentrations by irreversibly damaging different macromolecules such as protein lipid and DNA 1 . Plants because of their sessile nature are at greater risk of alterations in redox homeostasis resulting in oxidative stress 2 . .

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