310 T. HoRio, I. Sekuzu, T, Higashi and K. Okunuki 



by a certain factor, though the inhibitory action of cholate on the oxidase 

 activity has been considerably removed by the use of Emasol 4130 and Tween 

 80. Independent of this reactivation of the oxidase activity of the system 

 (cytochrome a + cytochrome c) by the use of the non-ionic detergents, the 

 molar ratio of cytochrome c to cytochrome a for the full oxidase activity is 

 approximately one. This may indicate that one mole of cytochrome a binds 

 one mole of cytochrome c to exhibit the oxidase activity. These findings 

 confirm that ox-heart muscle cytochrome oxidase activity is displayed by the 

 system, 'cytochrome a + cytochrome c\ It is therefore considered that the 

 behaviour of 'cytochrome a + cytochrome c' had been incorrectly expressed 

 as so-called cytochrome a^. 



The P-cytochrome oxidase purified to homogeneity shows a complex 

 absorption spectrum as if it contains c-type cytochrome and so-called cyto- 

 chrome «2- Based upon these facts, P-cytochrome oxidase appears to contain 

 more than one haem moiety. As indicated previously, in spite of the complex 

 absorption spectra, the oxidase preparation was estimated to contain two 

 iron atoms in each mole of the protein (88,000), but no copper, when the 

 experimental value was calculated for correction of a small amount of 

 impurities of the sample. 



Both mammalian and Pseudomonas cytochrome oxidase are thought to 

 consist of a complex of at least two cytochrome components or to be a protein 

 having at least two haems. 



Based upon the properties of cytochrome a and P-cytochrome oxidase, and 

 comparing cytochrome oxidase activity in both of them, the cytochrome 

 oxidase activity of the two systems may be visualized in the following way : 



In [cytochrome a -\- cytochrome c\ 



electron donor -> cytochrome q t^ ^cytochrome c 



cytochrome a ■ 



- oxygen 



where the brackets indicate the enzymic system (possibly binding of cyto- 

 chrome a and cytochrome c in a complex) capable of displaying cytochrome 

 oxidase activity. 

 In 'P-cytochrome oxidase' 



succinate -a P-cytochrome-(560)^P-cytochrome-554 l- DPNH 



I X w 



P-cytochrome-55 1 ^ P-blue protein 

 P-cytochrome 



oxidase 



'c-type' haem ^ 'g g-type' haem 



cyanide oxygen carbon monoxide 



