INHIBITION OF THE ALTERNATIVE OXIDASE STIMULATES H2O2 PRODUCTION IN PLANT-MITOCHONDRIA

The hypothesis that a non-coupled alternative oxidase of plant mitocho ndria operates as an antioxygen defence mechanism [Purvis, A.C. and Sh ewfelt, R.L., Physiol, Plant, 88 (1993) 712-718; Skulachev, V.P., Bioc hemistry (Moscow) 59 (1994) 1433-1434] has been confirmed in experimen ts on isolated soybean and pea cotyledon mitochondria, It is shown tha t inhibitors of the alternative oxidase, salicyl hydroxamate and propy l gallate strongly stimulate H2O2 production by these mitochondria oxi dizing succinate. Effective concentrations of the inhibitors proved to be the same as those decreasing the cyanide-resistant respiration, Th e inhibitors proved to be ineffective in stimulating H2O2 formation in rat liver mitochondria lacking the alternative oxidase, (C) 1997 Fede ration of European Biochemical Societies.