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Hydrogen peroxide generation by higher plant mitochondria oxidizing complex I or complex II substrates
Author(s) -
Braidot Enrico,
Petrussa Elisa,
Vianello Angelo,
Macrı̀ Francesco
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00616-x
Subject(s) - alternative oxidase , malonate , mitochondrion , oxidizing agent , hydrogen peroxide , chemistry , protonophore , glutamate receptor , electrochemical gradient , biochemistry , membrane , organic chemistry , receptor
The generation of H 2 O 2 by isolated pea stem mitochondria, oxidizing either malate plus glutamate or succinate, was examined. The level of H 2 O 2 was almost one order of magnitude higher when mitochondria were energized by succinate. The succinate‐dependent H 2 O 2 formation was abolished by malonate, but unaffected by rotenone. The lack of effect of the latter suggests that pea mitochondria were working with a proton motive force below the threshold value required for reverse electron transfer. The activation by pyruvate of the alternative oxidase was reflected in an inhibition of H 2 O 2 formation. This effect was stronger when pea mitochondria oxidized malate plus glutamate. Succinate‐dependent H 2 O 2 formation was ca. four times lower in Arum sp. mitochondria (known to have a high alternative oxidase) than in pea mitochondria. An uncoupler (FCCP) completely prevented succinate‐dependent H 2 O 2 generation, while it only partially (40–50%) inhibited that linked to malate plus glutamate. ADP plus inorganic phosphate (transition from state 4 to state 3) also inhibited the succinate‐dependent H 2 O 2 formation. Conversely, that dependent on malate plus glutamate oxidation was unaffected by low and stimulated by high concentrations of ADP. These results show that the main bulk of H 2 O 2 is formed during substrate oxidation at the level of complex II and that this generation may be prevented by either dissipation of the electrochemical proton gradient (uncoupling and transition state 4‐state 3), or preventing its formation (alternative oxidase). Conversely, H 2 O 2 production, dependent on oxidation of complex I substrate, is mainly lowered by the activation of the alternative oxidase.