INDUCED ENZYME FORMATION 



of an interesting device involving a relative plot in which in- 

 crement in enzyme is plotted against increment in cell mass. 

 This procedure has many advantages for studying relative 

 synthetic rates, since direct comparisons can be made between 

 slow- and fast-growing cultures. The data provided by certain 

 inducers yielded linear curves when plotted in this manner. 

 They suggest, therefore, that their findings are not consistent with 

 an autocatalytic mechanism. It should be noted, however, 

 that whereas the relative plot is extremely useful for the study of 

 relative rates of synthesis, it is a comparatively insensitive pro- 

 cedure for the kinetic examination of the early phases of the 

 induction. The time interval required for a definably measur- 

 able increment in mass could well be long enough to make im- 

 possible the examination of the kinetically interesting period of 

 induction. That this is not a remote possibility is easily shown 

 with yeast which form enzyme quite a bit more slowly than bac- 

 teria. If the data of yeast induction are plotted relatively, a 

 linear phase is observed. However, the early points show an 

 exponential departure from linearity. Were attention confined 

 solely to the later points, complete agreement with the data of 

 Monod, Pappenheimer, and Cohen-Bazire would have been 

 obtained. Finally, it must be noted that recent information on 

 inducer fixation (15) in the beta-galactosidase system is difficult 

 to reconcile with linear kinetics. 



A word may be interposed here about time linear kinetics 

 since a number of authors have taken its existence to nullify the 

 significance and interpretability of the autocatalytic type. It is 

 a fact that one can convert a synthetic reaction which is in- 

 herently autocatalytic to one which is linear with time, and the 

 possibility should neither occasion surprise nor engender con- 

 fusion. Thus, there is little doubt that under the usual con- 

 ditions the growth of bacterial populations is exponential. 

 Nevertheless, linear growth of a streptomycin-requiring strain 

 was reported by Schaefer (67). In discussing this observation 

 Monod (52) pointed out that a similar type of kinetics should be 

 obtainable artificially by establishing a constant limited supply 



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