INDUCED ENZYME FORMATION 



at rates comparable to those of intact cells. The beta-galac- 

 tosidase formed has been isolated in soluble form and purified. 

 These preparations are amenable to enzymatic resolution, their 

 enzyme-forming activity being abolished by RNase. This 

 treatment does not destroy them physically but selectively re- 

 moves 80 to 90 per cent of the RNA. 



It is evident that the search for a system which would per- 

 mit the further experimental probing of protein-synthesizing 

 systems is at present in an exciting but preliminary stage. There 

 seems little doubt, however, that a new era is being opened which 

 will ultimately permit a description in chemically defined terms 

 of the nature of the protein-synthesizing machinery. 



Summary and Concluding Remarks 



We have here surveyed the data which have accumulated 

 on the phenomenon of "enzymatic adaptation," with particular 

 emphasis on the eff"orts of the past decade. In view of the com- 

 plexity of the problem posed initially, and the difficulties which 

 could easily have hindered understanding or led to irrelevant 

 confusion, the progress which can be recorded is satisfying. 



Operationally diverse disciplines have provided the data 

 from which a picture of the enzyme-forming mechanism has 

 evolved. The kinetic, biochemical, and genetic information 

 on induced enzyme production all lead to and can be interpreted 

 in terms of one model. They suggest that the enzyme-forming 

 system is a complex between RNA, inducer, and enzyme. 



The problem has been brought to the point where further 

 questions must be posed in terms of the chemical structures and 

 reactive interrelations of the components identified. From the 

 experiments reviewed in the last section it would appear that the 

 systems needed for the experimental resolution of precisely such 

 questions are now well on the way to development. 



It seems likely at the present writing that the next decade 

 will provide the necessary answers. Attention can then be 

 profitably turned to the problem which initiated much of the 

 work described, i.e., what is the nature of gene function? 



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