RATES OF INHIBITION OF PURE ENZYMES 



555 



may be rewritten in terms of A;_2, the rate constant for the dissociation 

 of the ES complex: 



:i' 



(D + (S') 



1 — exp 





(12-35) 



TIME 



MIN 



Fig. 12-16. The rate curves for noncompetitive (I) and competitive (II) inhibition. 



iCf = 1 mM, ki = 10 min-^, and (I) = 5 xnM. For the competitive inhibition, 



Eq. 12-34 is plotted with K^ = 2 mM and (S) = 10 mM. Curve II shows the delaying 



effect of substrate on the development of inhibition. 



The following two situations may be considered: 



(D 



k,a) > k_,(8') 



k_,{8') > kAl) 



(D + (S') 



1 



exp 



exp 



1 + 



(!') 



k. 



K, 



(I) 



(S') 



(12-36) 



(12-37) 



Since (S') > (I), the value of A'^ must be much greater than k_2 for the first 

 situation to hold, whereas for the second situation the rate constants do 

 not have to differ appreciably. Corresponding to the two types of processes 

 discussed above, in the first case the rate of inhibition depends only on the 



