Taenia crassiceps metacestodes have cytochrome oxidase aa3 but not cytochrome o functioning as terminal oxidase

Abstract

In mitochondria obtained from Taenia crassiceps metacestodes, carbon monoxide difference spectra reveal signals characteristic of the classical mitochondrial oxidase, cytochrome aa 3, as well as signals suggesting the presence of ‘cytochrome o’. In the present work, using photodissociation spectrophotometry and analysis of the haem groups, we conclude that there is no haem O in these larvae, and that the only cytochrome that functions as terminal oxidase is cytochrome c oxidase, aa 3. At temperatures between −70 and −100°C, the energy of activation for CO reassociation with cytochrome a 3 was 10.5 kcal mol −1, and for oxygen binding 7.8 kcal mol −1.