Cytochrome c oxidase from Azotobacter vinelandii.

Although the terminal respiratory chain of Azotobacter has been the subject of several recent studies, the nature of the cytochrome oxidase portion is still somewhat obscure. Repaske (1) partially purified and characterized a soluble succinic dehydrogenase and succinoxidase system from Azotobacter z&elan&i. Wilson and Wilson (2) studied the soluble succinoxidase in Repaske’s preparation and demonstrated a bacterial cytochrome component in the cell-free preparation similar to but distinct from mammalian cytochrome c. They concluded that, although a succinate cytochrome c reductase is present which reduced mammalian cytochrome c, a cytochrome c oxidase (cytochrome ~3) is not concerned in the transport of electrons from succinate to oxygen. Vernon and Kamen (3) reported that the cytochrome oxidase of Azotobacter is specific for its own c type cytochrome and could not oxidize mammalian cytochrome c. Axotobacter cytochromes c4 and cg which resemble cytochrome c in several important properties have recently been purified and characterized (4, 5). These hemoproteins were specific for Azotobacter succinate and cytochrome oxidase activities and could not be linked to the cytochrome oxidase system from mammalian cells. The present paper describes the preparation and properties of a soluble cytochrome c oxidase from A. vinelandii. The enzyme preparation is capable of oxidizing reduced mammalian cytochrome c, heretofore not reported for a bacterial system, as well as reduced cytochromes c4 and c6 of Azotobacter. The oxidase is similar in a number of respects to the cytochrome c oxidase (cytochrome as) from mammalian tissues.