RATES OF INHIBITION OF PURE ENZYMES 



543 



The variation in the time course of inhibition with the rate constant 

 is shown in Fig. 12-5 where Eq. 12-12 is plotted at constant inhibitor con- 

 centration, the final inhibition being the same in each case. The changes 

 in the rate of inhibition with time are presented in Fig. 12-6 in which Eq. 

 12-13 is plotted. Finally, Fig. 12-7 shows the developments of inhibition 

 when the concentration of the inhibitor is varied, the terminal inhibition 

 now being different in every case. These curves serve to illustrate the typ- 

 ical behavior of a simple bimolecular inhibition reaction. 



TIME(MIN)- 



Fig. 12-5. Time courses of inhibition for different rate constants (Eq. 12-12). Ki = 1 



milf and (I) ^ 5 mM. Curve A, k\ = 100 rain-i; curve B, k^ = 30 min-i; curve C, 



i-j = 10 min-i; curve D, t^ = 1 min-^. 



When the inhibition progresses slowly, measurements of enzymic ac- 

 tivity are frequently made over intervals during which the inhibition is 

 changing significantly. In such cases, an average value for the inhibition 

 over the experimental period is obtained and we may now inquire into the 

 relationship between this average inhibition and the inhibition at a par- 

 ticular time. The mean inhibition over the interval from t^ to f.^is given by: 



ij'idt 



*2 'l 



(12-17) 



