Superoxide Dismutases (SOD) catalyze the dismutation of the superoxide radical (O₂ ^-) into hydrogen peroxide (H₂O₂) and elemental oxygen (O₂), and as such, provides an important defense against the toxicity of superoxide radical. SOD1 and SOD2-deficient mice spontaneously develop liver cancer and are prone to develop tumors, whereas over expression of SOD protects tumor cells from apoptosis.

In Trevigen’s Superoxide Dismutase Assay, ions generated from the conversion of xanthine to uric acid, and hydrogen peroxide by xanthine oxidase (XOD), convert NBT to NBT-diformazan. NBT-diformazan absorbs light at 550 nm. SODs reduce superoxide ion concentrations and thereby lower the rate of NBT-diformazan formation. The extent of reduction in the appearance of NBT-diformazan is a measure of SOD activity present in experimental samples. The assay is free of interference by other catalytic activities, and is ideal for assaying SOD in mammalian cell lysates. The kit contains the proper lysis buffer and the reagents needed for 100 experimental tests, 50 positive controls, and 50 negative controls. Unlike some other assay kits for SOD, this system is not greatly disturbed by trace metals. Each assay requires only about five minutes, and after a simple calculation, the percent inhibition of the formation of NBT-diformazan by SOD is converted to the
relative activity of the sample.