38 



2. THE KINETICS OF ENZYME REACTIONS 



It is difficult to determine the constants a, /?, and A", from experimental 

 data or even to prove that the mechanism is that given by Eq. 2-31 and 2-32 

 since other types of reaction can also lead to similar non-linearity in the 

 reciprocal plots of Ijv against 1/(S) (Fig. 2-7). For example, the kinetics 



2.5 



7.5 



/(s; 



Fig. 2-7. Reciprocal plots for the curves shown in Fig. 2-6. 



of urease indicated two active centers, but whether these were interacting 

 sites or independent sites with different kinetic parameters could not be 

 established (Kistiakowsky and Rosenberg, 1952). However, it is seen from 

 the reciprocal equation of 2-39 with /? = 1: 



+ 



aK 



1 



F,„ aK,{S) + (S)^ 



(2-41) 



that if llv is plotted against 1/(S)-, the slope near the 1/?' axis (where sub- 

 strate concentration is high) is a K^^"IV„i and the intercept 1/F,„. Since 



