ORIGIN OF ENZYMES 369 



significance in the rapidly flowing process of life. Thus the 

 direction in which any compound is altered in the course of 

 metabolism depends not only on the molecular structure of 

 the compound, but also on the enzymic activity of the proto- 

 plasmic proteins with which it becomes involved in the 

 course of metabolism. 



Thus, in enzymes, living bodies not only have powerful 

 accelerators of chemical processes, but also an extremely 

 efficient chemical apparatus which can direct these processes 

 along strictly determined channels. This is, in fact, the essen- 

 tial function of enzymes in living bodies, and it must be said 

 that enzymes are extremely efficient ' instruments ' for the 

 performance of this function. Their structure is amazingly 

 precisely adapted to the carrying out of this function in the 

 organisms. One has but to make a slight change in the struc- 

 ture of the enzyme complex, to rearrange or block one or 

 other of the chemical groups of its prosthetic part or to 

 disturb the structure of its protein component, and the 

 catalytic activity and specificity of the enzyme are markedly 

 diminished. Thus, even in enzymes, we can already see the 

 suitability of structure to function, the internal ' purposeful- 

 ness ' which is so characteristic of living matter in general. 



The study of the formation of enzymes in living bodies, 

 their biosynthesis, is, as yet, really only just beginning ; most 

 attention has so far been paid to the question of the ' adap- 

 tive ' origin of enzymes. "" We know very little about this 

 matter ; it is only clear that the biosynthesis of enzymes, like 

 that of proteins and the other components of protoplasm, 

 must occur by many stages. It is quite unnecessary that, in 

 the course of this biosynthesis, all the elements out of which 

 the enzyme complex is ' assembled ' should have been syn- 

 thesised by one and the same organism. They are very often 

 taken in ready-made from the environment in the form of 

 vitamins or parts of vitamins, essential amino acids, etc. 



How could such a highly developed catalytic apparatus 

 have arisen in the first place in the process of the directed 

 evolution of our original systems? 



In Chapter VI it was shown that the ability of enzymes to 

 carry out their functions in the organism, their great catalytic 

 activity and specificity, was primarily based on the strictly 



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