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



tension on the activity between both preparations. These facts indicate that 

 both preparations have the same kind of cytochrome oxidase. 



Table 1. Influence of addition of cytochrome c on the 

 oxidase-activity of cytochrome a 



Oxygen uptake was measured with a Warburg manometer at pH 7'4 and at 30°C. 



When Pseudomonas aeruginosa grows anaerobically in the presence of 

 nitrate, or under low oxygen tension (<20%) in the presence or absence of 

 nitrate, the cytochrome content of the cells is greater than for normally grown 

 cells and P-cytochrome oxidase can be purified from these cells as well as the 

 other respiratory components. If grown under higher oxygen tension, the 

 cells produce little or no cytochrome components, the respiration of the cells 

 is not inhibited by the inhibitors, and the oxidase cannot be purified from these 

 cells. Even with the cells grown anaerobically and under low oxygen tension, 

 the oxygen respiration of the cells is not always completely inhibited by 

 cyanide and carbon monoxide. The behaviour of hydroquinone oxidation by 

 the cell-free extract of the cells grown anaerobically in the presence of nitrate 

 towards various inhibitors is very similar to the oxygen respiration of the 

 living cells. From this cell-free extract, two different kinds of enzymes capable 

 of oxidizing hydroquinone can be purified : one is sensitive to cyanide and 

 carbon monoxide (P-cytochrome oxidase), and the other is resistant (P- 

 hydroquinone oxidase: Higashi, 1958). The former oxidase can rapidly 

 oxidize P-cytochrome-551, and P-blue protein, while the latter cannot perform 

 the oxidation. P-hydroquinone oxidase does not show any cytochrome-like 

 absorption spectrum, and its physiological function is not yet known except 

 that it can rapidly oxidize ascorbic acid as well as P-cytochrome oxidase. 



Properties of the Purified Preparations of Cytochrome a and P-cytochrome 

 Oxidase 



The cytochrome a contained in the purified preparation is easily reduced by 

 the addition of /j-phenylenediamine, as is indicated by an increase in extinction 

 of a- (605 mp,) and y- (444 m/<) absorption peaks. As shown in Fig. 1, the 



