[Quantitative method of determining the activity of zinc- and copper-dependent superoxide dismutase in biological...

The activity of superhydroxide dismutase was estimated by following rate of inhibition of non-enzymatic reduction of tetrazolium salt in reaction with superhydroxide ions, which were continuously generated in a photochemical system. The quantitative estimations were achieved by using para-nitrotetrazolium chloride, which was reduced to formazanes soluble in acetone. Formation of formazanes by the photochemical system (riboflavin + tetramethylethylene diamine + O2 + para-nitrotetrazolium chloride + light) in presence of biological material and cyanide was compared with formation of formazanes in absence of cyanide for specific estimation of Zn, Cu-dependent forms of superhydroxide dismutase. The rate of enzymatic cyanide sensitive inhibition of the photochemical formation of formazanes from paranitrotetrazolium chloride was determined by the activity of Zn, Cu-dependent superhydroxide dismutase in biological material and might be expressed in units of the activity -- un. ac. = 10/(0,026.% inhibition--1,3).