TRANSITION BETWEEN STEADY STATES 



387 



state is reached. The transition time, as defined above, will not be altered 

 but the rate during this period may never reach as low a level as the inhi- 

 bition on E2 would imply. Such behavior is illustrated in Fig. 7-40. 



Deviating behavior of the concentration of intermediate may be describ- 

 ed in the terminology of Denbigh et al. (1948). When the initial change 

 in an intermediate concentration exceeds that of the final steady-state 



time- 



Fig. 7-40. Illustration of the changes in 

 the concentrations of the intermediates 

 and in the rate of formation of D in a mo- 

 nolinear chain following inhibition of Eg. 



concentration, the system may be said to exhibit overshoot (Fig. 7-41A) 

 and if the concentration oscillates before reaching a final level, such be- 

 havior may be termed fluctuation (Fig. 7-41B). In some systems the con- 

 centration may initially change in an opposite direction to its final change 

 and the system is said to make a false start (Fig. 7-41C). Although first- 

 order kinetics were assumed (Denbigh et al., 1948), the treatment is qual- 

 itatively applicable to enzyme reactions. The rate of formation of product 

 may or may not follow such changes in intermediate concentration but the 

 same terminology may be applied to rate changes. The origin of these 

 phenomena is to be sought in the varying rates at which the different steps 

 in a multienzyme system can adapt to inhibition. The greater the complex- 

 ity of the system, the more oportunity there is for these deviations. Cyc- 

 lic, regenerative, and feedback systems are particidarly prone to overshoot 

 and fluctuation. Such behavior may be of importance not only in kinetic 

 measurements of inhibition but may be reflected in the functional response 

 of cells and tissues to an inhibitor. A simple specific inhibition may thus 



