SOD1 and brain neoplasm: In addition, endogenous enzymatic antioxidants, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase, glutathione-S-transferase (GST) etc. and non-enzymatic antioxidants such as GSH may potentially act as oxidative stress biomarkers for brain tumors.