tailieunhanh - Báo cáo khoa học: Seleno-independent glutathione peroxidases More than simple antioxidant scavengers

Glutathione peroxidases (GPXs, EC ) were first discovered in mam-mals as key enzymes involved in scavenging of activated oxygen species (AOS). Their efficient antioxidant activity depends on the presence of the rare amino-acid residue selenocysteine (SeCys) at the catalytic site. | IFEBS Journal REVIEW ARTICLE Seleno-independent glutathione peroxidases More than simple antioxidant scavengers Stéphane Herbette1 Patricia Roeckel-Drevet1 and Joel R. Drevet2 1 UMR 547-PIAF INRA Universite Blaise Pascal Aubiere Cedex France 2 UMR 6547-GEEM CNRS Universite Blaise Pascal Aubiere Cedex France Keywords free-radicalscavenger glutathione peroxidase oxidative stress selenocysteine thioredoxin Correspondence J. Drevet Universite Blaise Pascal CNRS UMR 6547 GEEM 24 avenue des Landais 63177 Aubiere cedex France Fax 33 4 73 40 52 45 Tel 33 4 73 40 74 13 E-mail Received 16 January 2007 revised 2 March 2007 accepted 7 March 2007 doi Glutathione peroxidases GPXs EC were first discovered in mammals as key enzymes involved in scavenging of activated oxygen species AOS . Their efficient antioxidant activity depends on the presence of the rare amino-acid residue selenocysteine SeCys at the catalytic site. Nonselenium GPX-like proteins NS-GPXs with a Cys residue instead of SeCys have also been found in most organisms. As SeCys is important for GPX activity the function of the NS-GPX can be questioned. Here we highlight the evolutionary link between NS-GPX and seleno-GPX particularly the evolution of the SeCys incorporation system. We then discuss what is known about the enzymatic activity and physiological functions of NS-GPX. Biochemical studies have shown that NS-GPXs are not true GPXs notably they reduce AOS using reducing substrates other than glutathione such as thioredoxin. We provide evidence that in addition to their inefficient scavenging action NS-GPXs act as AOS sensors in various signal-transduction pathways. Introduction Glutathione peroxidase GPX EC catalyses the reduction of H2O2 or organic hydroperoxides to water or the corresponding alcohols using reduced glutathione. GPX was discovered in 1957 1 as an enzyme that protects erythrocytes against oxidative damage. .

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