title: Flow-flash kinetics of O2 binding to cytochrome c oxidase at elevated [O2]: observations using high pressure stopped flow for gaseous reactants.
abstract: A high-pressure stopped-flow apparatus developed in our laboratories provides the capability to use dissolved gaseous reactants at elevated concentrations in solution (in equilibrium with gas pressures up to ca. 30 atm) for measurement of reaction kinetics. We have used this apparatus to follow the reaction of dioxygen with bovine cytochrome c oxidase following photolysis of the fully reduced CO ligated enzyme up to a dioxygen concentration of 16 mM. The observed rate dependence on [02] follows saturation kinetics and was fit to a limiting rate of 1.0 X 10(6) s(-1). This value is approximately the same as that for the thermal loss of CO to solution from the transient CuB bound state formed upon photolysis of the heme-CO complex. Implications for the mechanism of O2 binding and reduction by the heme-copper oxidases are discussed.
authors.affiliation: Biosciences and Biotechnology Group, Los Almos National Library, New Mexico 87545, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Bailey
authors.forename: C A
authors.initials: CA
authors.lastname: James
authors.forename: W H
authors.initials: WH
authors.lastname: Woodruff
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D005740:Gases; D006736:Horses; D007700:Kinetics; D008433:Mathematics; D009206:Myocardium / Q000201:enzymology; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D010782:Photolysis; D011312:Pressure; D013997:Time Factors; D014907:Whales
chemical_list: D005740:Gases; D009211:Myoglobin; D003576:Electron Transport Complex IV; D010100:Oxygen