Description
Glutathione peroxidases (Gpxs) are ubiquitously expressed proteins which catalyze the reduction of hydrogen peroxides and organic hydroperoxides by glutathione. There are several isoforms which differ in their primary structure and localization. The classical cytosolic /mitochondrial Gpx1 (cGpx) is a selenium-dependent enzyme, first of the Gpx family to be discovered. Gpx2, also known as gastrointestinal Gpx (GI-Gpx), is an intracellular enzyme expressed only at the epithelium of the gastrointestinal tract. Extracellular plasma Gpx (pGpx or Gpx3) is mainly expressed by the kidney from where it is released into the blood circulation. Phospholipid hydroperoxide Gpx4 (PH-Gpx) expressed in most tissues, can reduce many hydroperoxides including hydroperoxides integrated in membranes, hydroperoxy lipids in low density lipoprotein or thymine. All mammalian Gpx family members, except for the recently described Cys containing Gpx3 and epididymis-specific secretory Gpx (eGpx or Gpx5) isoforms, possess selenocysteine at the active site.
Because Gpx1 appears to have a major role in the prevention of oxidative stress, it may also be an important antiatherogenic enzyme. In mice, Gpx1 deficiency results in abnormal vascular and cardiac function and structure. From a clinical perspective, there is a report suggesting that low erythrocyte Gpx1 activity identifies patients with coronary artery disease who are at the high risk for cardiovascular events and that measurement of Gpx1 activity provides additional information on risk and might be useful in identifying patients who would benefit from preventive antioxidant treatment