CYTOCHROME OXIDASES OF PSEUDOMONAS 

 AERUGINOSA AND OX-HEART MUSCLE, AND 

 THEIR RELATED RESPIRATORY COMPONENTS 



By T. HoRio, I. Sekuzu, T. Higashi* and K. Okunuki 



Department of Biology, Faculty of Science, University of Osaka, 



Osaka 



Keilin and Hartree (1939) observed that their cytochrome oxidase prepara- 

 tion from ox-heart muscle contained a cytochrome component spectro- 

 photometrically similar to cytochrome a, and they reported that the 

 component differed from cytochrome a in the manner in which the component 

 was sensitive to carbon monoxide. They thought that this component might 

 be identical with cytochrome oxidase, calling it cytochrome a^. Thereafter 

 in most reports, cytochrome oxidase preparations were described as con- 

 taining both cytochromes a and ^3. These two components have, however, 

 not yet been separately purified. It is well known that the cytochrome 

 oxidase preparation can oxidize cytochrome c, but not /7-phenylenediamine, 

 cysteine, or ascorbic acid, unless cytochrome c is present. Smith (1956) has 

 found that the purified cytochrome a can be partially reduced by /7-phenylene- 

 diamine. Okunuki et al. (1958) found that their preparation of purified 

 cytochrome a showed the typical activity of cytochrome oxidase if cytochrome 

 c was present, and that the preparation contained no spectrophotometrically 

 detectable cytochrome component other than cytochrome a. 



Negelein and Gerischer (1934), and Fujita and Kodama (1934) discovered 

 that cytochrome Wg was widely distributed among bacteria, and that it was 

 autoxidizable and could combine with carbon monoxide and with cyanide. 

 These properties led to the assumption that cytochrome a^ had the function 

 of a cytochrome oxidase. There are, however, some reports (Chance, 1953; 

 Smith, 1955) that cytochrome a^ may be the terminal respiratory enzyme in 

 Acetobacter pastewianum ; these argue against the hypothesis that cytochrome 

 ^2 acts as the respiratory enzyme of the bacteria. However, neither cytochrome 

 Qi nor cytochrome a, had been purified; moreover, it was not known in 

 either case which substances could be oxidized by these cytochromes. Horio 



* Present address: Department of Biochemistry, Medical School, University of Osaka, 

 Osaka, Japan. 



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