A novel aco-type cytochrome-c oxidase from a facultative alkalophilic Bacillus: purification, and some molecular and enzymatic features

Abstract

A novel aco-type cytochrome-c oxidase was highly purified from the facultative alkalophilic bacterium, Bacillus YN-2000, grown at pH 10. The enzyme contained 9.0 nmol heme a/mg protein. It contained 1.23 mol of protoheme, 1.06 mol of heme c, 2.0 g atoms of copper, 2.5 g atoms of iron, and 1.8 g atoms of magnesium per mol of heme a. The enzyme molecule seemed to be composed of two subunits with Mrs of 52,000 and 41,600. On the basis of these results, the enzyme seemed to contain one molecule each of heme a, protoheme, and heme c per minimal structural unit (Mr, 93,600). Only protoheme among the three kinds of hemes in the enzyme reacted with CO and CN-. Heme a did not react with CO; cytochrome a3 did not seem to be present in the enzyme. The enzyme oxidized 314 mol of horse ferrocytochrome c per heme a per sec at pH 6.5 and the catalytic activity was 50% inhibited by 7.65 microM KCN. The enzymatic activity was found to be optimal at pH 6.0.