Evidence for Distinct Electron Transfer Processes in Terminal Oxidases from Different Origin by Means of Protein Film Voltammetry

[Image: see text] Cytochrome aa(3) from Paracoccus denitrificans and cytochrome ba(3) from Thermus thermophilus, two distinct members of the heme–copper oxidase superfamily, were immobilized on electrodes modified with gold nanoparticles. This procedure allowed us to achieve direct electron transfer between the enzyme and the gold nanoparticles and to obtain evidence for different electrocatalytic properties of the two enzymes. The pH dependence and thermostability reveal that the enzymes are highly adapted to their native environments. These results suggest that evolution resulted in different solutions to the common problem of electron transfer to oxygen.