146 



S. S. COHEN 



activity was established on a molecular basis, i.e., its turnover number was 

 determined. It was thereby shown th t each molecule of penicillui fixed was 

 not consumed in induction and could induce the formation of at least 10 

 molecules of enzyme. In this instance an inducer molecule appears to be 

 metabolized and organized within an enzyme-forming site in such a way that 

 the amino acids which are assembled emerge as a protein with a unique 

 catalytic specificity. This phenomenon may be represented as shown in 

 formula (X). 



Cell boundary 



Inducer 



Metabolism 



Gjmplex of "I 



inducer and I 



protein - forming I 



Amino 

 acids 



site 



Enzyme 



(X) 



The linear rate of penicilUnase synthesis in the B. cereus system and the 

 linear "differential" rate of enzyme synthesis may be taken to suggest that, 

 in induction, the protein-forming sites are fully formed and merely activated 

 by the addition of the appropriately metabolized inducer. This interpretation 

 has been questioned by Spiegelman and Campbell (1956), who have critically 

 discussed the existing data. Their own genetic studies had led to the view 

 that induction, at least in its early stages, involves an autocatalytic S3mthesis 

 or activation of templates at the enzyme-forming site. It is considered to be 

 significant in this regard that once enzyme formation has begun it becomes 

 increasingly more resistant to ultraviolet irradiation than the effect of this 

 treatment when inducer has just been added (Pollock, 1953; Halvorson and 

 Jackson, 1956). This result imjihes that the process of organization of the 

 enzyme-forming system is more sensitive to ultraviolet irradiation than the 

 direct synthesis of enzyme from precursors. It is possible then that the 

 nucleic acids are more concerned with the development of the former stage 

 than in the latter. On the other hand, since nucleoproteins are more resistant 

 to such irradiation than the free nucleic acids (Siege! et al., 1956) this result 

 may merely reflect the change in the template from a free to combined state. 



5. On Cell Permeability and Enzyme Synthesis 



The analysis of the formation of enzyme-forming systems in microorgan- 

 isms has recently been comphcated by the discovery that an intracellular 

 accumulation of inducer must precede enzjmae synthesis and that the develop- 

 ment of an accumulating system has in its turn all of the features of the 

 induced biosynthesis of proteins. This discovery, although comphcating some 

 problems, clarifies others, such as the question of why many bacteria which 



