Determination of superoxide dismutase activity
The activity of the SOD enzyme was determined using the method previously reported by McCord and Fridovich (McCord and Fridovich, 1969). This method involves preventing the SOD enzyme from reducing cytochrome-C by superoxide radicals formed in the xanthine/xanthine oxidase system. The activity of the SOD enzyme is based on measuring this inhibition. The amount of SOD that inhibited this reaction by 50% was considered to be 1 Unit (U). SOD enzyme activity was measured at 550 nm by kinetic monitoring, and the results were expressed as U/mg protein.