Cytochrome c Oxidase of the Cyanobacterium Phormidium foveolarum

Phormidium foveolarum was grown with nitrate or ammonia as nitrogen source. With ammonia present respiration increased by a factor of 4 due to increase of cytochrome c oxidase. The inhibition of respiration by cyanide was measured during the growth period, indicating that only one terminal oxidase is present in Phormidium foveolarum . Cytochrome c oxidase from ammoniagrown filaments was solubilized and purified on phenylsuperose and by anion exchange 100-fold compared to the crude cell extract. The difference spectrum (oxidized minus reduced) shows absorption peaks at 417 nm, 5 1 4 -5 2 0 nm. 550 nm and 605 nm. These maxima, together with a low inhibition constant for cyanide (AT, = 0.4 î m) and a higher one for azide ( ^ = 1.75 mM) are interpreted in terms of an aa,-type cytochrome c oxidase present containing noncovalently-bound cytochrome c.