538 



12. RATES OF INHIBITION 



that may be used to characterize the rate at which the inhibition develops. 

 It is commonly found that the rate of the enzymic or metabolic reaction 

 measured falls exponentially in the presence of the inhibitor, in which case 

 the variation of the rate with time would be given by a curve as in Fig. 12-2 

 and expressed by an equation of the type: 



Vi = Vf + {Vo - Vf)e- 



(12-1) 



Fig. 12-2. Exponential development of inhibition from the initial uninhibited rate, 



v^, to the final equilibrium rate in the presence of the inhibitor, Vf (Eq. 12-1), r^ — 100, 



Vf = 30, and a = 0.1 min^^. 



where v^ is the initial uninhibited rate, Vj the final equilibrium rate, v^ 

 the rate at any particular time, and a is a constant. Transposing and taking 

 the logarithm of each side of the equation, it is found that: 



log{r, 



log(ro 



2.3 



(12-2) 



so that a plot of log {i\ — v^) against t will give a straight line with a slope 

 of — a/2.3 as in Fig. 12-3. The exponential nature of the inhibition must. 



