tailieunhanh - Báo cáo Y học: Two GPX-like proteins from Lycopersicon esculentum and Helianthus annuus are antioxidant enzymes with phospholipid hydroperoxide glutathione peroxidase and thioredoxin peroxidase activities

This study investigated the enzymatic function of two putative plant GPXs, GPXle1 from Lycopersicon esculentum and GPXha2 from Helianthus annuus, which show sequence identities with the mammalian phospholipid hydroperoxide glutathione peroxidase (PHGPX). Both purified recombinant proteins expressed in Escherichia coli show PHGPX activity by reducing alkyl, fatty acid and phospholipid hydroperoxides but not hydrogen peroxide in the presence of glutathione. | Eur. J. Biochem. 269 2414-2420 2002 FEBS 2002 doi Two GPX-like proteins from Lycopersicon esculentum and Helianthus annuus are antioxidant enzymes with phospholipid hydroperoxide glutathione peroxidase and thioredoxin peroxidase activities Stephane Herbette1 Catherine Lenne1 Nathalie Leblanc1 Jean-Louis Julien1 Joel R. Drevet2 and Patricia Roeckel-Drevet1 1UMR 547-PIAF INRAịUniversité Blaise Pascal Aubiere France 2UMR 6547-GEEM CNRS Universite Blaise Pascal Laboratoire Epididyme Maturation des Gametes Aubiere France This study investigated the enzymatic function of two putative plant GPXs GPXle1 from Lycopersicon esculentum and GPXha2 from Helianthus annuus which show sequence identities with the mammalian phospholipid hydroperoxide glutathione peroxidase PHGPX . Both purified recombinant proteins expressed in Escherichia coli show PHGPX activity by reducing alkyl fatty acid and phospholipid hydroperoxides but not hydrogen peroxide in the presence of glutathione. Interestingly both recombinant GPXle1 and GPXha2 proteins also reduce alkyl fatty acid and phospholipid hydroperoxides as well as hydrogen peroxide using thioredoxin as reducing substrate. Moreover thioredoxin peroxidase TPX activities were found to be higher than PHGPX activities in terms of efficiency and substrate affinities as revealed by their respective Vmax and Km values. We therefore conclude that these two plant GPX-like proteins are antioxidant enzymes showing PHGPX and TPX activities. Keywords antioxidant free radical scavenger tomato sunflower. In all aerobic organisms reactive oxygen species ROS originating from the metabolism of oxygen constitute a threat to virtually any cell constituent. In plants it has been shown that environmental stresses can cause an increase in ROS levels 1-4 . Despite their noxious effects on proteins lipids and nucleic acids which could ultimately lead to cell death ROS in a more controlled manner can participate in early signaling .

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