26 



Inside the Living Cell 



But in the amino acid chains of proteins, which were described in 

 Chapter I, we have seen that there exists the possibility of almost 

 innumerable different patterns. Nature has apparently taken advan- 

 tage of this to produce the many specialized patterns of enzymes, but 



/'compound^ 



Stage I. The compound 



approaches the enzyme surface 



ENZYME SURFACE 



Stage ll.The compound combines 

 with the enzyme surface 



COMPOUND BROKEN 



Stage III. The compound 



is broken into two parts 



\_/PRODUCTS 



ENZYME SURFACE 



Stage IV. The products are 



released from the enzyme surface 



FIG. 4. How an enzyme acts. Characteristic of enzyme action is the high 

 degree of specificity, i.e., a close fit between the enzyme and the compound 

 it acts on 



at present we are ignorant as to the nature of the patterns which 

 constitute the active groupings in the enzymes. 



It is an extraordinary fact — and an unexpected one — that the 

 simplest organisms seem to be provided with enzymes which are 

 very similar to those of the highest organisms. Even the simplest 

 forms of Hfe which have survived to this day have practically all the 

 types of enzymes which we find in the higher animals. It is possible 

 that new types may be discovered in the higher animals but so far 



