Purification and Properties of Cytochrome c-553 and Cytochrome B-560 from Tetrahymena pyriformis*

Abstract

Cytochrome c-553 and cytochrome B-560 were highly purified from the protozoan, Tetrahymena pyriformis. Cytochrome c (553, T. pyriformis) possesses an absorption maximum at 410 mμ in the oxidized form, and maxima at 414, 523 and 553 mμ in the reduced form. The ratio of A_{414 mμ}(reduced)/A_553mμ(reduced) of the cytochrome is 5.35, and the millimolar extinction coefficient of the α-peak is 27.4. The midpoint redox potential of the cytochrome is about +0.25 volt at pH 7.0. The cytochrome c is an acidic protein on the basis of its affinity for diethylaminoethylcellulose and is not precipitated by saturation with ammonium sulphate. It reacted slowly with Pseudomonas cytochrome oxidase [EC 1.9.3.2], but did not react with cow cytochrome oxidase [EC 1.9.3.1]. Cytochrome B (560, T. pyriformis) shows an absorption peak at 411 mμ in the oxidized form, and peaks at 424, 529 and 560 mμ in the reduced form. This cytochrome is autoxidizable, and combines with carbon monoxide and cyanide, but not with azide, and does not show any peroxidase activity.