In plants, especially in chloroplasts, superoxide radical is generated when an electron is transferred to dimolecular O2 due to decreased activity of Photosystem I. The superoxide (O2-) radical accumulation is more rampant in plants exposed to abiotic stresses due to oxidation of photosystem components. Excessive superoxide radical accumulation will lead to oxidative damage to the cellular macromolecules. The ubiquitous superoxide dismutases (SODs) represent critical enzymatic antioxidant system present in cells, which can catalyze the disproportion of superoxide (O2-) radical rapidly into hydrogen peroxide (H2O2) and molecular oxygen. Depending on the metal cofactor present, the plant SODs are classified into Cu/ZnSOD, MnSOD, and FeSOD. The activity of SODs can be quantified zymographically. Additionally, using this method, different classes of SODs can be distinguished by using H2O2, KCN, and NaN3.
Keywords: Characterization of SOD; Classes of SODs; Electrophoresis; NBT; Riboflavin; SOD activity.