Abstract
1. The oxygenated form of cytochrome a was demonstrated to be distinct from both the oxidized and reduced forms, as well as from a mixture of these two forms.
2. Another type of the oxidized form of cytochrome a was postulated to occur in the functional state.
3. The dynamic equilibrium between these three forms of cytochrome a, that is between another type of the oxidized form and the oxygenated and reduced forms, is thought to be established in the steady state in a system consisting of a reductant, cytochrome a, cytochrome c and molecular oxygen.
4. The possible role of cytochrome c in the cytochrome oxidase system was suggested and a scheme was given for the cyclic change of cytochrome a in its functional state.
