Journal
EUROPEAN JOURNAL OF BIOCHEMISTRY
Volume 269, Issue 9, Pages 2414-2420Publisher
BLACKWELL PUBLISHING LTD
DOI: 10.1046/j.1432-1033.2002.02905.x
Keywords
antioxidant; free radical scavenger; tomato; sunflower
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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 V-max and K-m values. We therefore conclude that these two plant GPX-like proteins are antioxidant enzymes showing PHGPX and TPX activities.
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