Protects the hemoglobin in erythrocytes from oxidative breakdown. In platelets, plays a crucial role of glutathione peroxidase in the arachidonic acid metabolism (PubMed:9195979). 2 glutathione + H2O2 = glutathione disulfide + 2 H2O (12S)-hydroperoxy-(5Z,8Z,10E,14Z)-eicosatetraenoate + 2 glutathione = (12S)-hydroxy-(5Z,8Z,10E,14Z)-eicosatetraenoate + glutathione disulfide + H2O Homotetramer. Interacts with MIEN1. Expressed in liver, kidney and lung. During periods of oxidative stress, Sec-47 may react with a superoxide radical, irreversibly lose hydroselenide and be converted to dehydroalanine. Mutants are healthy, fertile and show no increased sensitivity to hyperoxia. In the absence of Sod1, Gpx1 in the liver undergoes a 40% reduction in catalytic activity as a result of the decomposition of Sec-47 to dehydroalanine. Belongs to the glutathione peroxidase family. PubMed:2771650 sequence was originally thought to originate from human. Number of sequencing artifacts.