Abstract

The specificities for cytochrome c of the aa3-type cytochrome c oxidase were studied with enzymes derived from Thiobacillus novellas, Nitrobacter agilis, Paracoccus denitrificans and the cow in reaction with the cytochromes c from 5 prokaryotes and 7 eukaryotes. The T. novellus enzyme reacted most rapidly with the cytochromes c of Candida krusei, tuna and bonito as well as T. novellus cytochrome c; the specificity for cytochrome c of the N. agilis enzyme was similar to that of the T. novellus enzyme. The bovine enzyme reacted rapidly with all the eukaryotic cytochromes c tested. The P. denitrificans enzyme showed a specificity similar to that of the bovine enzyme, except that it reacted rapidly with P. denitrificans cytochrome c, while the bovine enzyme reacted with it very poorly. All four kinds of enzymes showed an extremely limited reaction with Pseudomonas aeruginosa cytochrome c.

The amino acid composition of subunit I of the N. agilis enzyme resembled that of the bovine enzyme, while the compositions of their subunits II were different. On the basis of these results, an evolutionary relationship between bacterial and eukaryotic enzymes was discussed.

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