Glutathione peroxidase 4 (GPX4) is a selenocysteine-containing glutathione peroxidase that is encoded by the GPX4 gene in humans and protects cellular membranes from oxidative damage.{48903,48904} It is a monomeric protein consisting of a thioredoxin motif and a selenocysteine-glutamine-tryptophan catalytic triad that reduces lipid hydroperoxides, including phospholipid, polyunsaturated lipid, and sterol hydroperoxides, to non-toxic lipid alcohols. During this process, the active site selenocysteine becomes oxidized and must subsequently be replenished by the reducing substrate glutathione (GSH).{48904} There are three isoforms of GPX4, mitochondrial mGPX4, cytosolic cGPX4, and nuclear nGPX4/snGPX4, that are expressed in all tissue types in rats, with the highest mRNA levels observed in testes.{48903,48904,48906} GPX4 is a key regulator of ferroptosis that inhibits ferroptotic cell death by preventing iron-dependent accumulation of toxic lipid reactive oxygen species.{48904} Mutations in GPX4 have been found in patients with Sedaghatian-type spondylometaphyseal dysplasia (SSMD), and silencing of Gpx4 in mice is embryonic lethal.{48905,48904} Cayman's GPX4 Polyclonal Antibody can be used for immunohistochemistry (IHC) and Western blot (WB) applications. The antibody recognizes GPX4 at 20 kDa from human, mouse, rat, and porcine samples.