INDUCED ENZYME FORMATION 



would be the formation of enzyme. As a consequence, the 

 kinetics of enzyme formation would be autocatalytic independ- 

 ently of the actual kinetic details of the enzyme-forming process. 

 Although eminently plausible, it was pointed out (76,90) that an 

 argument of this nature could not be used to explain away the 

 autocatalytic formation of hydrogenlyase, the functioning of 

 which could hardly yield sufficient energy for protein synthesis. 

 Further, this criticism turned out on subsequent investigation 

 (35) not to be applicable to the system against which it was 

 directed. An examination of the relation between the kinetics 

 of enzyme formation and the rate of energy supply revealed that 

 alpha-glucosidase synthesis is exponential only when the rate at 

 which energy is delivered exceeds a certain critical value. Below 

 this it is linear with time. Thus, if one actually performs the 

 induction in such a manner (e.g., anaerobically, with highly 

 purified maltose) as to insure that the inducer is the sole energy 

 source, linear and not autocatalytic kinetics are obtained for the 

 early phases of the induction. The original experiments were 

 performed aerobically under conditions in which a relatively 

 high endogenous respiration was the principal energy source, 

 the contribution of inducer metabolism being negligible. 



Monod and Cohn (55) have quite correctly emphasized 

 that wherever possible, the complications which can attend the 

 utilization of an energy-generating inducer should be avoided by 

 the use of what they call "gratuitous induction." Conditions of 

 gratuity require the use of a nonutilizable inducer and a neutral 

 noninductive energy source. The discovery that alpha-methyl- 

 glucoside is a nonutilizable inducer of the alpha-glucosidase 

 system made it possible to reexamine the question of the kinetics 

 of alpha-glucosidase synthesis under gratuitous conditions. 

 Again exponential kinetics were obtained (35). 



There exists another interesting possibility which, if it ob- 

 tained, would make interpretation of the kinetics of induction 

 difficult and uncertain. This stems from the fact that in following 

 the appearance of enzyme in a population cell, an over-all 

 average property is measured. Were the process of enzyme 



133 



