276 EXISTENCE OF A REDUCING ENDO-ENZYME 



It would seem to be the ferment which starts the process 

 of internal respiration, oxidase that which continues and 

 completes it. 



IX. THE CHEMICAL POWERS OF REDUCTASE. 



In conclusion I should like to point out the true reducing 

 character of the reductase of animal tissues. 



(a) In the first place it is a typical deoxidizer in that it 

 removes oxygen from osmium tetroxide and from such sub- 

 stances as oxyhaemoglobin, which is fully reduced, and 

 methaemoglobin, which is reduced to the oxy condition. 



(b) Substances containing oxygen, but not in a form 

 wholly removable, can be reduced from the higher to the 

 lower state, as when sodium nitrate is reduced to sodium 

 nitrite, ( 25 ) or when sodium indigo-disulphonate and sodium 

 alizarine-sulphonate are respectively reduced to their pale 

 chromogens. 



(c) The reductase can also reduce metallic salts con- 

 taining no oxygen from their higher to their lower forms, as 

 when ferric chloride is reduced to ferrous chloride( 15 ). Here 

 the change involved is the removal of an ionic charge from the 

 t.rivalent ferri-ion which becomes the di-valent ferro-ion. 



(d) Finally, certain pigments containing no oxygen 

 such as soluble Prussian blue and methylene blue are reduced 

 to the pale or white chromogenic conditions of the di-potassio- 

 ferrous-ferrocyanide and methylene white respectively. 



In all these reductions, the endo-enzyme is behaving 

 after the manner of an inorganic reducing agent in an alkaline 

 medium. 



[The expenses of this research were met by a grant 

 from the Government Grants Committee of the Royal Society, 

 which is hereby gratefully acknowledged.] 



