Cytochrome a-type terminal oxidase derived from Thiobacillus novellus. Molecular and enzymatic properties.

Cytochrome a-type terminal oxidase was purified from Thiobacillus novellus to an electrophoretically homogeneous state and some of its properties were studied. The enzyme shows absorption peaks at 428 and 602 nm in the oxidized form, and at 442 and 602 nm in the reduced form. The CO compound of the reduced enzyme shows peaks at 431 and 599 nm. The enzyme has 1 mol of haem a and 1 g-atom of copper per 55600 g and is composed of two kinds of subunit, of 32000 and 23000 daltons, respectively. The enzyme reacts rapidly with tuna, bonito and yeast cytochromes c as well as with T. novellus cytochrome c, while it reacts slowly with horse and cow cytochromes c. The reduction product of oxygen catalysed by the enzyme is water.