Bacillus subtilis expresses two kinds of haem‐A‐containing terminal oxidases

Abstract

The expression of two different aa₃‐type cytochrome oxidases is demonstrated in Bacillus subtilis. One of them (denoted caa₃‐605), was predicted by DNA‐sequencing of Bacillus cytochrome oxidase genes, but has not been found previously. It contains covalently bound haem C in subunit II and is very similar to the enzyme previously described in the thermophilic bacterium PS3. The other oxidase (denoted aa₃‐600) deviates from most known oxidases of aa₃ type, and is probably identical with the oxidase described by de Vrij et al. [de Vrij, W., Azzi, A. & Konings, W. N. (1983) Eur. J. Biochem. 131, 97–103]. It shows no immunological cross‐reactivity to the PS3 enzyme and differs from this spectroscopically; it contains no Cu_A and does not oxidise cytochrome c despite of its haem‐A chromophores. It catalyses oxidation of quinols, which is proposed to be its physiological function.