[HARRIS] A REDUCING ENDO-ENZYME 137 



7X. 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 deoxidiser in that it removes 

 oxygen from osmium tetroxide and from such substances as oxy- 

 ha^moglobin, which is fully reduced, and methsemoglobin,'^ 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, ^^ or when sodium indigo- 

 disulphonate and sodium alizarine-sulphonate are respectively reduced 

 to their pale chromogens. 



(c) The reductase can also i educe metallic salts containing no 

 oxygen from their higher to their lower forms, as when ferric chloride 

 is reduced to ferrous chloride. ^^ Here the change involved is the 

 removal of an ionic charge from the trivalent ferri-ion which becomes 

 the di-valent ferro-ion. 



(d) Finally, certain pigments containing no oxygen, such as sol- 

 uble 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 of L )ndon, which 

 is hereby gratefully acknowledged.) 



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