Assaying for superoxide dismutase activity: Some large consequences of minor changes in conditions

Most assays for superoxide dismutase depend upon competition between the enzyme and some indicating scavenger for O2−. We have investigated the effects of experimental variables on assays based upon the use of either ferricytochrome c or nitro blue tetrazolium. Our results should help investigators to avoid the numerous potential pitfalls which necessarily surround these assay methods.