OXIDASES, PEROXIDASES, AND CATALASE 79 



of ordinary charcoal. From hemin, in turn, branch out even more 

 complex systems of still greater catalytic activity, such as the hemo- 

 chromogens and hemochromogen-charcoal adsorbates, reaching the 

 climax in nature's own products, the hemin enzymes. Upon linking 



IRON CATALYSTS 



Homogeneous Sysfems 

 Inorganic Fe- Salts 



Heferogeneous Sysfems 



IRON OXIDES (MITTASCH) 



Iron Salt -Charcoal Adsorbate 



Charcoal 



I 



Inorganic Fe-Complexes 



Organic Fe-Complexes 

 i 



Blood or Hemin Charcoal 



HEMIN 



Hemm- Charcoal Adsorbate 



'N- Bases 

 Hemochromogens — 



i 



Hemochrcmogen-Charcoal Adsorbate 



M/croheferogeneous Sysfems 



"Globm 



* Coll. Fe(0H)3 



* 

 -* Hemoglobin 



i 



►Active Proteins 



[enzymes 



>Catalose, Peroxidase, Oxidase 



Figure 1. — A family tree of iron catalysts 



protoferriheme IX to a specific protein, the enzyme catalase is created 

 which is capable of splitting 10^ moles of hydrogen peroxide per sec- 

 ond under optimum conditions, in spite of the fact that because of the 

 screening of the iron atom, the geometrical requirements for success- 

 ful collisions with the substrate have become much more strin- 

 gent (20). This spectacular increase in activity is, however, gained at 

 the price of a decrease in the number of substrates which may be 

 attacked by a given enzyme. Hemin itself shows marked oxidatic, 



