Isolation of a b-Type Cytochrome Oxidase from Membranes of the Phototrophic Bacterium Rhodopseudomonas capsulata

Abstract

A cytochrome oxidase (EC 1.9.3.1) was solubilized from the membrane fraction of aerobically grown cells of Rhodopseudomonas capsulata by treatment with Triton X-100. The enzyme was purified 160 fold by chromatography on DEAE-Sepharose CL-6B and affinity chromatography on cytochrome c-thiol activated Sepharose 4B. The purified enzyme has a pH-optimum at 8.5 and a temperature optimum at 35 °C. The ap­ parent K_m for reduced horse cytochrome c is 24 μм (at pH 8 and 30 °C). The purified cytochrome oxidase was 50% inhibited by 1.5 μм KCN and 10 μм NaN₃. The purified enzyme contained one polypeptide of m_r 65,000 and 6-type cytochrome.