INDUCED ENZYME FORMATION 



With yeast the presence of an external nitrogen supply greatly 

 suppressed the severity and the extent of this interaction, and in- 

 deed, under certain circumstances simultaneous formation to 

 two otherwise interfering enzymes was made possible. 



Although these interactions were discovered relatively early 

 in the renewed investigation of the phenomenon of enzymatic 

 adaptation, their detailed significance remains to be delineated. 

 Nevertheless, at the time, they were interpreted to suggest a 

 competition for some commonly required nitrogenous material 

 and therefore implied the existence of a precursor not as yet 

 specified as to its ultimate enzymatic function. To these findings 

 may be added those which established that the induction of 

 enzymes requires the participation of a functional and utilizable 

 energy-generating mechanism. Agents such as 2,4-dinitro- 

 phenol (50), sodium azide (74), and arsenate (93) which pre- 

 vent the utilization of energy generated by metabolism also 

 inhibit the induction of enzyme activity. 



The importance of these early observations derived essen- 

 tially from the fact that they made unlikely one quite obvious and 

 attractive possibility of explaining the phenomenon of induced 

 enzyme formation. This hypothesis suggests that the mech- 

 anism involved is one akin to the activation of trypsinogen to 

 trypsin. Of course, the fact that energy is required for the induc- 

 tion precludes at once any simple application of this concept. 

 In addition, such a model would suppose the preexistence in a 

 cell of inactive forms of enzymes already fully determined as to 

 their specificity and their function. The inhibitory interactions 

 observed would be difficult to explain under these circumstances. 

 Although observations of this nature could not definitely decide 

 the issue, they clearly encouraged the search for a nitrogenous 

 precursor not as yet restricted in its specificity and potentially 

 convertible into more than one kind of enzym.e molecule. 



In designing experiments which seek to reveal the nature of 

 this precursor, one can be guided by the fact that, in principle, 

 three mechanisms of enzyme synthesis can be written down. 

 They are as follows: 



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