All aerobic living organisms utilize dioxygen as an essential component for three main roles that are necessary to maintain life: the production of energy, the oxidative metabolism of endogenous compounds, and the defense of the organism against various kinds of infections [1,2] (Figure 1). In many species, the production of energy necessary for the cells utilizes the reduction of O2 into H2O in mitochondria, this highly exothermic reaction being coupled with adenosine triphosphate (ATP) production. The last step of this four-electron reduction of O2 is performed by cytochrome oxidase, a system containing two hemes and three copper ions.