title: Low-temperature kinetics of the reaction of oxygen and solubilized cytochrome oxidase.
abstract: The reaction of solubilized cytochrome oxidase in the fully reduced state with O2 at low temperatures reveals components with characteristics similar to those observed with the membrane-bound oxidase, namely compounds A and B, which are proposed to be 'oxy' and 'peroxy' compounds respectively. Similar species are identified in both solubilized and membrane-bound oxidases; the reaction velocity constant for the reation with O2 and the dissociation constant are decreased 2-3-fold in the solubilied preparation as compared with the membrane-bound species, owing to decreased reactivity towards O2 in the former. The oxidase prepared in the mixed-valence state shows the distinctive absorption band characteristic of compound C, identified in the membrane-bound oxidase. The assignment of the alpha, beta, gamma and near-i.r. absorption bands to possible valence states of these compounds is made.
mesh_terms: D003080:Cold Temperature; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D008566:Membranes; D010100:Oxygen / Q000378:metabolism*; D013055:Spectrophotometry, Infrared; D013057:Spectrum Analysis; D013696:Temperature
chemical_list: D003576:Electron Transport Complex IV; D010100:Oxygen