SOD1 and chronic obstructive pulmonary disease: SOD enzymes include CuZnSOD, MnSOD (SOD2), and SOD3, SOD3 levels in induced sputum supernatants of COPD patients were higher compared to nonsmokers [29], and in our study, both total SOD and CAT activity were increased in COPD rat model, it may be a compensatory mechanism to counteract the acceleration of oxidative stress.