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THE ROLE OF ENZYME REGULATION 

 IN METABOLISM 



Arthur B, Pardee 



UNIVERSITY OF CALIFORNIA, BERKELEY 



The problem of metabolic regulation ' 



The ability to achieve and maintain specific end results of form and 

 function amid a variety of perturbing influences, physical and chemi- 

 cal, is one of the greatest wonders of living things. It must be apparent, 

 to a chemist at least, that to understand how a living cell regulates its 

 processes and adjusts itself automatically to influences in its environ- 

 ment, it is necessary to describe the external controlling factors and the 

 cell's response processes in chemical terms. 



As a beginning in this direction it seems profitable to look into the 

 phenomena which at present can be discussed in the language of 

 chemistiy. Such processes are the formation of the large and small 

 molecules which are the substance and the currency of living cells. We 

 will speak here of "regulation" and "regulated metabolism," by which 

 we will mean production of molecules only to the extent to which they 

 are to be used for growth or function. Can we discover the methods of 

 regulation whereby these billions of molecules are formed each hour 

 in the amounts required for one cell's efficient growth and function ac- 

 cording to the pattern of its kind? Some of these regulatory mecha- 

 nisms have been discovered only in the last few years, and it will be the 

 objective of this article to present and discuss them. 



Since enzymes catalyze chemical reactions in living cells, the rate 

 at which each reaction proceeds must depend both on the number of 

 catalyzing enzyme molecules and on the rate at which each enzyme 

 molecule can act. Correspondingly, there are two possible sorts of 

 regulatory processes: one kind determines the number of molecules of 



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