title: Photochemical action spectra indicate that cytochrome a/a3 is the predominant haemoprotein terminal oxidase in Acanthamoeba castellanii.
abstract: 1. Room-temperature CO-reduced minus reduced difference spectra of intact cells of Acanthamoeba castellanii show the presence of CO-reacting haemoproteins in cells from the early-exponential, late-exponential and stationary phases of growth. 2. The relative rates of reaction with CO of the two haemoproteins differ; that of cytochrome a/a3 with CO is complete within 1 min of bubbling with CO, whereas that of cytochrome b takes longer than 90 min. 3. Photochemical action spectra reveal cytochrome a/a3 as the predominant haemoprotein oxidase at all stages of growth. 4. It is concluded that the alternative oxidases known to be present in these organisms are not cytochromes.
mesh_terms: D000656:Amoeba / Q000166:cytology / Q000201:enzymology*; D000818:Animals; D002248:Carbon Monoxide; D002455:Cell Division; D003576:Electron Transport Complex IV / Q000378:metabolism*; D010777:Photochemistry; D013053:Spectrophotometry
chemical_list: D002248:Carbon Monoxide; D003576:Electron Transport Complex IV