Figure 2. Analysis of O₂^•− dismutation to H₂O₂ by intact mitochondria.

H₂O₂ formation was measured by monitoring horseradish-peroxidase-catalysed H₂O₂-dependent oxidation of p-hydroxyphenylacetate. Reactions were carried out in sucrose/Tris buffer, pH 7.4, containing 5 m-units/ml xanthine oxidase, 50 μM xanthine, 5 m-units/ml horseradish peroxidase and 1 mM p-hydroxyphenylacetate, with (a) no further additions; (b) 4 μM bovine Cu,Zn-superoxide dismutase; (c) intact mitochondria (100 μg of protein/ml); or (d) mitochondrial intermembrane space content preparation (10 μg of protein/ml).