556 



12. RATES OF INHIBITION 



rate constant for dissociation of the ES complex (ES dissociates slowly) 

 and in the second case it depends only on the rate constant for the com- 

 bination of the inhibitor with the enzyme (ES dissociates rapidly). In the 

 cholinesterase inhibition studies of Goldstein, k^il) = 0.913 and k^^i^') = 

 20.8, vSo that Eq. 12-37 would be applicable without serious error. The rate 



10 



Logarithmic plots of the rate curves for noncompeti- 

 tive and competitive inhibition (or for competitive inhibition in 

 the presence and absence of the substrate). Same conditions as 

 in Fig. 12-16. 



of inhibition in this case is markedly slowed by the substrate because there 

 is so little free enzyme available and not because the dissociation of the 

 ES complex is limiting the rate. 



Attention must be called to the fact that in Eqs. 12-35 to 12-37, the in- 

 hibition approaches the value (!')/[(!') + (S')] as a final equilibrium state. 

 This should actually be (!')/[(!') + (S') + 1] (see Eq. 3-28). The reason 



