May protect the virus and component of infected cells from oxidative damage by peroxides whose formation may be stimulated by infection. 2 glutathione + H2O2 = glutathione disulfide + 2 H2O During periods of oxidative stress, Sec-64 may react with a superoxide radical, irreversibly lose hydroselenide and be converted to dehydroalanine. This enzyme has been acquitted by lateral transfer from its human host and has retained 74% identity with cellular GPX1. Belongs to the glutathione peroxidase family.