Voltammetric detection of superoxide production by photosystem II

Oxygen radicals play both pathological and physiological roles in biologica l systems, The detection of such radicals is difficult due to their transie nt nature and the presence of highly efficient antioxidant mechanisms. In p lants the physiological role of oxygen is twofold, oxygen is produced by th e oxidation of water and consumed as an electron acceptor. The direct invol vement of oxygen in photosynthetic events exposes the photosynthetic appara tus to a high probability of damage by oxygen radicals. We report here a di rect, simple and rapid method for the measurement of superoxide in vitro ba sed on voltammetric detection. It has potential applications for other in v itro systems investigating superoxide production. We show that in addition to the well established production of superoxide from photosystem I, under reducing conditions superoxide is also produced by photosystem II, probably from the QA site. (C) 1999 Federation of European Biochemical Societies.