INDUCED ENZYME FORMATION 



assumed to drive the reaction in the direction of precursor con- 

 version into enzyme. This complexing concept leads to several 

 predictions, the experimental violation of any one of which 

 would require either its revision or complete abandonment. 

 We may list some of these as follows : 



7. Substances which can complex with enzymes should be 

 effective inducers. 



2. Substances shown to be incapable of complex formation 

 with a given enzyme likewise should be unable to induce this 

 enzyme. 



3. The dissociation constant of the substance measured in 

 terms of its inductive effect on enzyme synthesis should be com- 

 parable in magnitude to the value obtained in experiments in 

 which the constant is derived from complexing properties of 

 the inducer with enzyme. 



It should be noted that the term "complex formation" 

 employed here is meant to subsume both the specific type, 

 characterized by combination between an enzyme and its sub- 

 strate or competitive inhibitor, and the nonspecific type, repre- 

 sented by a complex between an enzyme and a noncompetitive 

 inhibitor. Thus, proof that an inducer does not form a specific 

 complex with enzyme does not eliminate it as an enzyme com- 

 plexant, since it leaves open the possibility of nonspecific com- 

 plex formation. There is no a priori reason for believing that 

 nonspecific combinations cannot function in the process of 

 enzyme synthesis. 



It is difficult to provide convincing exceptions to the second 

 deduction mentioned, involving as it does only negative proper- 

 ties. However, violations of both (7) and {3) have been found. 

 Thus, Lederberg (45) exhibited a mutant of E. coli which fails to 

 respond to lactose as an inducer of beta-galactosidase, despite the 

 fact that lactose is a substrate and therefore a specific com- 

 plexant. 



Monod, Cohen-Bazire, and Cohn (54) subjected these con- 

 siderations to the first systematic and thorough analysis. They 

 revealed that thio-phenyl-beta-D-galactoside, although a potent 



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