188 



5. DETERMINATION OF MECHANISMS AND CONSTANTS 



mechanism was involved with Kj^ = 2.04 X 10~^ M. This is surprising since 

 a simple EI complex is not formed in this case, so that the general validity 

 of this approach is still in doubt. The plot is shown in Fig. 5-25. 



T 



Fig. 5-25. Krupka-Laidler plot for the inhibition of 



chymotrypsin by DFP at pH 8.1. (From Krupka and 



Laidler, 1959.) 



SUGGESTIONS FOR PLOTTING AND DETERMINATION OF 



CONSTANTS 



It will perhaps be useful to conclude this chapter with some general 

 suggestions concerning the types of experimental data desirable, the ap- 

 proach to different methods of plotting, and the interpretation of the re- 

 sults. It is evident without discussion that the reliability of mechanistic 

 interpretations and the accuracy of the calculated constants depend di- 

 rectly on the accuracy of the experimental data. In much quantitative 

 scientific investigation it is required that multiple runs be performed so 

 that mean values and their significance can be determined. However, in 

 enzyme work it has been the rule that plots are made and constants cal- 

 culated from a single experimental series. Most of the methods used for 

 enzyme rate determination involve appreciable errors and greater accu- 



