Seleno-independent glutathione peroxidases. More than simple antioxidant scavengers.
Glutathione peroxidases (GPXs, EC 1.11.1.9) 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.
Herbette
Stéphane
S
UMR 547-PIAF, INRA/Université Blaise Pascal, Aubière Cedex, France.
Roeckel-Drevet
Patricia
P
Drevet
Joël R
JR
D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D012643:Selenium / Q000737:chemistry* / Q000378:metabolism* / Q000502:physiology
D000975:Antioxidants; D016166:Free Radical Scavengers; D005979:Glutathione Peroxidase; D012643:Selenium