Superoxide dismutase (SOD) activity

The measurement of SOD activity was based on the inhibition of the radical superoxide reaction with adrenalin as described by McCord and Fridovich [17]. In this method, SOD present in the sample competes with the detection system for radical superoxide. One SOD unit is defined as the amount of enzyme able to slow down the speed of adrenalin oxidation in 50%. The oxidation of adrenalin leads to the formation of a colored product adrenochrome that might be detected by spectrophotometry. SOD activity was determined by measuring the speed of adrenochrome formation observed at 480 nm in a reaction medium containing glycine-NaOH (50 mM, pH 10.0) and 1 mM adrenalin. Specific activity was expressed as SOD units per mg of protein.