NADH Induces the Generation of Superoxide Radicals in Leaf Peroxisomes

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Abstract
In peroxisomes isolated from pea leaves (Pisum sativum L.) the production of superoxide free radicals (O2−) by xanthine and NADH was investigated. In peroxisomal membranes, 100 micromolar NADH induced the production of O2− radicals. In the soluble fractions of peroxisomes, no generation of O2− radicals was observed by incubation with either NADH or xanthine, although xanthine oxidase was found located predominantly in the matrix of peroxisomes. The failure of xanthine to induce superoxide generation was probably due to the inability to fully suppress the endogenous Mn-superoxide dismutase activity by inhibitors which were inactive against xanthine oxidase. The generation of superoxide radicals in leaf peroxisomes together with the recently described production of these oxygen radicals in glyoxysomes (LM Sandalio, VM Fernández, FL Rupérez, LA del Río [1988] Plant Physiol 87: 1-4) suggests that O2− generation could be a common metabolic property of peroxisomes and further supports the existence of active oxygen-related rôles for peroxisomes in cellular metabolism.