Analysis of superoxide dismutase activity

Measuring the activity of superoxide dismutases (SODs), the enzymes responsible for maintaining the steady state level of hydrogen peroxide, is challenging because the substrate is unstable at physiological pH and it reacts with itself. Fortunately the rate of reaction with dismutase is far greater than the rate of self reaction. As described in this unit, this activity can be measured indirectly based on competition between SOD and an indicator molecule that reacts avidly with superoxide to produce a measurable change in absorption, thus it is possible to measure total SOD activity or that of CuZn-SOD and MnSOD. The activity can also be measured by an activity stain applied to thin-film agarose or native polyacrylamide gels.