Cytochrome Oxidases <>/ Pseudomonas Aeruginosa 309 



Table 3. Comparison of specificity between pseudomonas cytochrome 

 oxidase and ox-heart cytochrome oxidase to various electron-donating 



substances 



Oxygen consumption was measured by use of a Warburg manometer. Reactions with P-cytochrome 

 oxidase were at 30'C in 004 M phosphate buffer of pH 60, and reactions using ox-heart cytochrome 

 oxidase were carried out in the presence of cytochrome c at 15°C in 001 m phosphate buffer of pH 70 



containing 2-3 % and 20 % oxygen, respectively. The K^^ values for P-cyto- 

 chrome-551, and P-blue protein are 1-9 x lO^'^M and 3-9 x 10~^m, respec- 

 tively, at 18°C and at pH 5-1, which is the optimal pH for both reactions. 

 The turnover numbers for the oxidations of hydroquinone, P-cytochrome-551, 

 and P-blue protein are 44 moles of oxygen consumed per mole of oxidase per 

 min at pH 6-4 (optimum) and at 30'^C, 87 moles at pH 5-1 and at 18°C, and 

 100 moles at pH 5-1 and at 18°C, respectively. 



DISCUSSION 



The cytochrome a preparation which is free of other cytochromes, shows 

 the same cytochrome oxidase activity as does the Keilin-Hartree particulate 

 preparation, which is free of cytochrome c but contains all other cytochromes 

 and the succinate oxidase system. Moreover, the cytochrome oxidase activity 

 of the cytochrome a preparation is identical in all its properties with the 

 description of the animal cytochrome oxidase (so-called cytochrome ^3), 

 except for the turnover number. Based on the results of the oxidation and 

 reduction of the cytochrome a present in the cytochrome a preparation, it is 

 certain that cytochrome a displays a direct and essential function in the cyto- 

 chrome oxidase activity of the purified a preparation. Because the cytochrome 

 oxidase activity of the purified cytochrome a has a turnover-number one-third 

 that of the original extract, it seems likely that the cytochrome oxidase 

 activity of 'cytochrome a + cytochrome c' is still being partially inhibited 



