Glutathione peroxidase (GPx) (EC 1.11.1.9) is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage.owever, glutathione peroxidase 4 knockout mice die during early embryonic development. Some evidence, though, indicates reduced levels of glutathione peroxidase 4 can increase life expectancy in mice.