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Zinc ions inhibit oxidation of cytochrome c oxidase by oxygen
Author(s) -
Aagaard Anna,
Brzezinski Peter
Publication year - 2001
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(01)02299-2
Subject(s) - chemistry , cytochrome c oxidase , kinetics , zinc , proton , electron transport complex iv , oxygen , cytochrome , histidine , oxidase test , ion , enzyme , heme a , redox , medicinal chemistry , photochemistry , stereochemistry , crystallography , inorganic chemistry , biochemistry , organic chemistry , physics , quantum mechanics
Cytochrome c oxidase is a membrane‐bound enzyme that catalyses the reduction of O 2 to H 2 O and uses part of the energy released in this reaction to pump protons across the membrane. We have investigated the effect of addition of Zn 2+ on the kinetics of two reaction steps in cytochrome c oxidase that are associated with proton pumping; the peroxy to oxo‐ferryl (P r →F) and the oxo‐ferryl to oxidised (F→O) transitions. The Zn 2+ binding resulted in a decrease of the F→O rate from 820 s −1 (no Zn 2+ ) to a saturating value of ∼360 s −1 with an apparent K D of ∼2.6 μM. The P r →F rate (∼10 4 s −1 before addition of Zn 2+ ) decreased more slowly with increasing Zn 2+ concentration and a K D of ∼120 μM was observed. The effects on both kinetic phases were fully reversible upon addition of EDTA. Since both the P r →F and F→O transitions are associated with proton uptake through the D‐pathway, a Zn 2+ ‐binding site is likely to be located at the entry point of this pathway, where several carboxylates and histidine residues are found that may co‐ordinate Zn 2+ .