Cytochrome Oxidases of Pseudomonas Aeruginosa 3 1 5 



STEPWISE REDUCTION OF PSEUDOMONAS CYTOCHROME OXIDASE 

 1.90 1,1 1 I .11- 



1 w 



000 

 450 500 550 600 650 700 



WAVELENGTH in m;j 



Fig. 1. 



Slater: Referring to the point raised by Morton, I believe that cytochromes a and a^ 

 refer to different haemoproteins, both containing haem a as prosthetic group. It is 

 probable that the two proteins are physically closely linked in the mitochondria, and 

 it may not be possible physically to separate them. All purified preparations of 

 cytochrome c oxidase which have been described contain what Keilin and Hartree 

 described in 1939 as cytochrome a and a^, i.e. a part of the a and y-bands do not 

 react with KCN, CO, or Oj, while another part does react with these compounds. 

 That part which reacts is called cytochrome a^, that part which does not is called 

 cytochrome a. The spectra observed in the presence of substrate, under various 

 conditions, are 



anaerobic 



CO 



anaerobic + HCN 



aerobic + HCN 





CO 



0++ + fl3++CN 

 a++ + a3+++CN 



If you wish to regard cytochrome oxidase as a single haemoprotein (called cytochrome 

 a), you will find it difficult to interpret the spectral changes under the above-mentioned 

 conditions, without postulating that part of cytochrome a reacts with CO, KCN and 

 Oo, and part does not. Why not, therefore, retain the name cytochrome a^ for that 

 part which reacts with these reagents, and cytochrome a for that which does not. 

 Smith : I do not think that the question of the existence of two separate haemoproteins 

 in the particulate cytochrome oxidase can be decided, since we do not have a water- 

 soluble system. The important point is whether there are two separate reactive haem 

 groups in the complex. 



H.E. — VOL. I — w 



