Features of Organization and Mechanism of Catalysis of Two Families of Terminal Oxidases: Heme-Copper and bd-Type

Terminal oxidases of aerobic respiratory chains catalyze the transfer of electrons from the respiratory substrate, cytochrome c or quinol, to O 2 with the formation of two H 2 O molecules. There are two known families of these membrane oxidoreductases: heme-copper oxidase superfamily and bd -type oxidase family (cytochromes bd ) found in prokaryotes only. The redox reaction catalyzed by these enzymes is coupled to the generation of proton motive force used by the cell to synthesize ATP and to perform other useful work. Due to the presence of the proton pump, heme-copper oxidases create the membrane potential with a greater energy efficiency than cytochromes bd . The latter, however, play an important physiological role that enables bacteria, including pathogenic ones, to survive and reproduce under adverse environmental conditions. This review discusses the features of organization and molecular mechanisms of functioning of terminal oxidases from these two families in the light of recent experimental data.