ENZYMES 



Table 2 



41 



It has been held by many workers that certain metals, 

 notably iron and copper, are essential constituents of 

 enzymes ; some enzymes, such as catalase, peroxidase, 

 tyrosinase and ascorbic dehydrogenase, certainly contain 

 these metals, but very active ^^reparations of others have 

 been obtained which are quite free from them. 



Catalase can be split, by treatment with dilute acid, 

 to give two inactive fragments, a colloidal protein carrier 

 and the prosthetic group on which the activity of the 

 intact enzyme depends. The prosthetic group is identical 

 with the hsem of haemoglobin, since if it is coupled with 

 globin from the animal from which the enzyme was 

 derived it yields the haemoglobin characteristic of that 

 species. 



Tyrosinase and ascorbic dehydrogenase contain copper 

 in the form of haemocyanin, analogous to the iron 

 porphyrin compound haemoglobin. 



The flavo -protein enzymes such as Warburg's " yellow 

 respiratory enzyme," which occurs in bottom yeast and 

 in Lactobacillus delhruchii for instance, (/-amino-oxidase, 

 occurring in liver or kidney, and diaphorase present in 



