Cytochrome c oxidase

The enzyme cytochrome c oxidase (PDB 2OCC, EC 1.9.3.1 ) is a large transmembrane protein found in the mitochondrion and is the terminal electron acceptor in the electron transfer chain, taking 4 reducing equivalents from cytochrome c and converting molecular oxygen to water. In the process, it translocates protons, helping to establish a chemiosmotic potential that the ATP synthase then uses to synthesize ATP.

Summary reaction:

4 Fe⁺²-cytochrome c + 4H⁺ + O₂ → 4 Fe⁺³-cytochrome c + H₂O.

The complex is a large lipoprotein composed of several metal prosthetic sites and 13 protein subunits. In mammals, 10 subunits are nuclear in origin and 3 are synthesized mitochondrially. The complex contains 2 cytochromes, the a and a₃ cytochromes, and two copper centers, the Cu_A and Cu_B centers. In fact, the cytochrome a₃ and Cu_B are a binuclear center that is the site of oxygen reduction. The mechanism of action of this large complex is still an active research topic.

Further information

The Cytochrome Oxidase home page