STUDIES ON CYTOCHROME OXIDASE SYSTEM OF LIGHT-ANAEROBICALLY AND DARK-AEROBICALLY GROWN CELLS OF RHODOPSEUDOMONAS CAPSULATA

The aerobic oxidase-system from dark-aerobically and light-anaerobically grown Rps. capsulata was investigated. The particulate fraction sedimented from ultrasonic extracts by 140,000 g-centrifugation, catalyzed the oxidation of NADH, succinate and reduced cytochrome c (horse heart). The oxidase activities of the particles from dark-aerobically grown cells were in the range of 0.10-0.38 μmoles O2/min x mg protein and were usually ten times as high as the oxidase activities from light-grown cells. The particles contain cytochromes of b-type and c-type. Cytochrome of a-type could be detected neither in the particles from light-grown nor in the particles from dark-grown cells. The highest values of the relation between cytochrome b and cytochrome c were found in the particles from darkaerobically grown cells. The cytochrome oxidase reacts with cytochrome c (horse heart), DCPIP and TMPD. The km-values are 5×10-5m, 1.5×10-4m, or 2×10-4m, respectively. The cytochrome oxidase exhibits a broad pH-optimum in the range of pH 8.5-9.5. Saturation of the oxidase with O2 is observed at a partial pressure of 15-20% O2. The oxidase is inhibited by KCN and NaN3 (half inhibition at 10-5m), but not by CO. The particles from dark-aerobically and light-anaerobically grown cells catalyze phosphorylation of ADP in the dark coupled to the oxidation of succinate with maximum P/O-values of 0.3. © 1969 Springer-Verlag.