Cytochrome Oxidase and Peroxide Metabolism

Orii, Yutaka

doi:10.1007/978-1-4684-5835-0_16

Cited by 2 publications

(1 citation statement)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It was shown earlier [9][10][11][12][13] that under anaerobic conditions, COX catalysed slow oxidation of cytochrome c upon addition of hydrogen peroxide. Under aerobic conditions, H2O2 could not compete with oxygen to any significant extent and contribution of peroxidatic oxidation of cytochrome c was barely visible [14]. Similar conclusions were arrived at in the pre-steady state studies of the Amsterdam group [15][16][17].…”

Section: Introductionsupporting

confidence: 81%

Proton pumping by cytochrome c oxidase is coupled to peroxidase half of its catalytic cycle

et al. 1997

View full text Add to dashboard Cite

The four-electron reaction cycle of cytochrome oxidase is comprised of an eu-oxidase phase in which the enzyme receives the first two electrons and reduces oxygen to bound peroxide and a peroxidase phase in which the peroxy state formed in the eu-oxidase half of the cycle is reduced by the 3rd and 4th electrons to the ferryl-oxo state and oxidized form, respectively. Here we show that the ferrocyanide-peroxidase activity of cytochrome c oxidase incorporated in phospholipid vesicles is coupled to proton pumping. The H+/e ratio for the ferrocyanide-peroxidase partial reaction is twice higher than for the overall ferrocyanide-ox/rfase activity and is close to 2. These results show that proton pumping by COX is confined to the peroxidase part of the enzyme catalytic cycle (transfer of the 3rd and 4th electron) whereas the eu-oxidase part (transfer of the first two electrons) may not be proton pumping.

show abstract

Section: Introductionsupporting

confidence: 81%

Proton pumping by cytochrome c oxidase is coupled to peroxidase half of its catalytic cycle

et al. 1997

View full text Add to dashboard Cite

show abstract

Ferrocyanide-peroxidase activity of cytochrome c oxidase

Konstantinov

Vygodina

Capitanio

et al. 1998

Biochimica et Biophysica Acta (BBA) - Bioenergetics

View full text Add to dashboard Cite

Redox interaction of mitochondrial cytochrome c oxidase (COX) with ferrocyanide/ferricyanide couple is greatly accelerated by polycations, such as poly-l-lysine [Musatov et al. (1991) Biological Membranes 8, 229-234]. This has allowed us to study ferrocyanide oxidation by COX at very high redox potentials of the ferrocyanide/ferricyanide couple either following spectrophotometrically ferricyanide accumulation or measuring proton uptake associated with water formation in the reaction. At low [ferrocyanide]/[ferricyanide] ratios (Eh values around 500 mV) and ambient oxygen concentration, the ferrocyanide-oxidase activity of COX becomes negligibly small as compared to the reaction rate observed with pure ferrocyanide. Oxidation of ferrocyanide under these conditions, is greatly stimulated by H2O2 or ethylhydroperoxide indicating peroxidatic reaction involved. The ferrocyanide-peroxidase activity of COX is strictly polylysine-dependent and is inhibited by heme a3 ligands such as KCN and NaN3. Apparently the reaction involves normal electron pathway, i.e. electron donation through CuA and oxidation via heme a3. The peroxidase reaction shows a pH-dependence similar to that of the cytochrome c oxidase activity of COX. When COX is preequilibrated with excess H2O2, addition of ferrocyanide shifts the initial steady-state concentrations of the Ferryl-Oxo and Peroxy compounds towards approximately 2:1 ratio of the two intermediates. It is suggested that in the peroxidase cycleferrocyanide donates electrons to both P and F intermediates with a comparable efficiency. Isolation of a partial redox activity of COX opens a possibility to study separately proton translocation coupled to the peroxidase half-reaction of the COX reaction cycle. Copyright 1998

show abstract

Cytochrome Oxidase and Peroxide Metabolism

Cited by 2 publications

References 19 publications

Proton pumping by cytochrome c oxidase is coupled to peroxidase half of its catalytic cycle

Proton pumping by cytochrome c oxidase is coupled to peroxidase half of its catalytic cycle

Ferrocyanide-peroxidase activity of cytochrome c oxidase

Contact Info

Product

Resources

About