A CYTOCHROME-O-TYPE OXIDASE OF THE THERMOPHILIC BACTERIUM PS3 GROWN UNDER AIR-LIMITED CONDITIONS

A cytochrome o-type oxidase from the thermophilic bacterium PS3 grown under air-limited conditions was purified by ion-exchange chromatography in the presence of a non-ionic detergent. The enzyme was composed of three subunits (60, 30, and 16 kDa) and seemed to contain two molecules of heme b as prosthetic groups. It contained no detectable copper. The reduced enzyme showed absorption bands at 426 and 558.5 nm, and a characteristic spectral change upon binding CO. It oxidized several cytochromes c and artificial dyes such as N, N, N1, N1-tetramethyl-p-phenylenediamine and phenazonium methosulfate at appreciable rates. Its Km for O2 was low (0.09 μM). It was capable of transmembrane electron transfer, because when reconstituted into liposomes, it generated a membrane potential upon oxidation without pumping protons. © 1990 COPYRIGHT, 1990 BY THE JOURNAL OF BIOCHEMISTRY.