Reactivity Characteristics of Cytochrome £,

The mechanism whereby cytochrome c oxidase catalyses elec--tron transfer from cytochrome c _ to oxygen remains an unsolved problem, Polarographic and spectrophotometric activity measure-ments of purified, particulate and soluble forms of beef heart mitochondrial cytochrome c oxidase presented in this thesis con-firm the following characteristics of the steady-state kinetics with respect to cytochrome c: (1) oxidation of ferrocytochrome c is first order under all conditions, (2) The relationship between sustrate concentration and velocity is of the Michaelis-Menten type over a limited range of substrate, concen-trations at high ionic strength, (3) The reaction rate is independent from oxygen concentration until very low levels of oxygen, (4) "Biphasic " kinetic plots of enzyme activity as a function of substrate concentration are found when the rang