Cytochrome c oxidase

Written By: Ehsan Jahandarpour

The enzyme cytochrome c oxidase or Complex IV, EC, is a large transmembrane protein complex found in bacteria, archaea, and mitochondria of eukaryotes. It is the last enzyme in the respiratory electron transport chain of cells located in the membrane. It receives an electron from each of four cytochrome c molecules and transfers them to one oxygen molecule and four protons, producing two molecules of water and releasing a lot of energy without breaking bonds of an organic fuel. In addition to binding the four protons from the inner aqueous phase, it uses the energy of oxygen to translocate another four protons across the membrane, increasing the transmembrane difference of proton electrochemical potential, which the ATP synthase then uses to synthesize ATP.