GPX1 and neoplasm: In tumor mitochondria, the upregulation of glutamate dehydrogenase 1 (GDH1) in glutamine metabolism promotes an increase in the levels of α-ketoglutarate (α-KG) and the subsequent intermediate metabolite fumarate, which activates and binds to the ROS scavenging enzyme glutathione peroxidase 1 (GPX1) to protect against oxidative damage (43).