title: The "ferrous-oxy" intermediate in the reaction of dioxygen with fully reduced cytochromes aa3 and bo3.
abstract: We have studied the reactions with oxygen of two terminal oxidases, cytochrome c oxidase from mitochondria and cytochrome bo3 from Escherichia coli. In each case, flow-flash methodology was used to react the fully reduced enzyme with a high concentration of oxygen (1 mM), and absorbance changes were recorded for a number of separate wavelengths in the alpha-band (visible) region. In both enzymes, an early kinetic phase could be resolved, corresponding to the binding of oxygen to produce a ferrous-oxy heme intermediate. In cytochrome c oxidase, this intermediate appears with a time constant of 10 microseconds; its spectrum has a peak at 595 nm (relative to the unliganded reduced enzyme). In cytochrome bo3, the ferrous-oxy intermediate, resolved by optical absorbance spectroscopy for the first time, appears with a time constant of 11 microseconds and has a broad maximum near 570 nm.
authors.affiliation: Department of Medical Chemistry, University of Helsinki, Finland. mverkhov@penger.helsinki.fi
authors.forename: M I
authors.initials: MI
authors.lastname: Verkhovsky
authors.forename: J E
authors.initials: JE
authors.lastname: Morgan
authors.forename: A
authors.initials: A
authors.lastname: Puustinen
authors.forename: M
authors.initials: M
authors.lastname: Wikström
mesh_terms: D000818:Animals; D002417:Cattle; D003573:Cytochrome b Group; D003580:Cytochromes / Q000737:chemistry* / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D006418:Heme; D007501:Iron; D007700:Kinetics; D008929:Mitochondria, Heart / Q000201:enzymology; D008956:Models, Chemical; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; C083850:cytochrome bo3, E coli; D006418:Heme; D007501:Iron; D003576:Electron Transport Complex IV; D010100:Oxygen