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pH changes associated with cytochrome c oxidase reaction with H 2 O 2 Protonation state of the peroxy and oxoferryl intermediates
Author(s) -
Konstantinov A.A.,
Capitanio N.,
Vygodina T.V.,
Papa S.
Publication year - 1992
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 - 10.1016/0014-5793(92)81412-f
Subject(s) - chemistry , cytochrome c oxidase , protonation , cytochrome c , photochemistry , oxidase test , cytochrome , superoxide dismutase , superoxide , electron transport complex iv , medicinal chemistry , electron transport chain , stereochemistry , enzyme , biochemistry , mitochondrion , organic chemistry , ion
pH changes associated with the mitochondrial cytochrome oxidase reaction with H 2 O 2 have been studied. In the presence of forricyanide or Tris‐phenanthroline complex of Co III as electron acceptors, reaction or H 2 O 2 with the oxidized cytochrome oxidase is accompanied by a steady proton release with a rate constant of ca. 3 M −1 s −1 at pH 6.8. The acidification is completely inhibited by superoxide dismutase and its pro‐steady‐state kinetics correlates with that of the oxoferryl compound (F) accumulation. Apparently, the proton release is linked to superoxide generation by cytochrome oxidase under these conditions. In the presence of superoxide dismutase and without the electron acceptors, the H 2 O 2 ‐induced transitions of cytochrome oxidase from the oxidized to the peroxy (P) and from the peroxy to the oxoferryl state are not associated with any significant proton release or uptake. The results point to the following mechanism of O − 2 generation and protonation states of the cytochrome oxidase compounds P and F: