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. 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.
Herbette
Stéphane
S
UMR 547-PIAF INRA/Université Blaise Pascal, Aubière, France.
Lenne
Catherine
C
Leblanc
Nathalie
N
Julien
Jean-Louis
JL
Drevet
Joël R
JR
Roeckel-Drevet
Patricia
P
D000975:Antioxidants / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006368:Helianthus / Q000201:enzymology*; D008054:Lipid Peroxides / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000201:enzymology*; D009363:Neoplasm Proteins; D010544:Peroxidases / Q000378:metabolism*; D054464:Peroxiredoxins; D010743:Phospholipids / Q000378:metabolism*; D020122:tert-Butylhydroperoxide / Q000378:metabolism
D000975:Antioxidants; D008054:Lipid Peroxides; D009363:Neoplasm Proteins; D010743:Phospholipids; D020122:tert-Butylhydroperoxide; D010544:Peroxidases; D054464:Peroxiredoxins; D005979:Glutathione Peroxidase