Inhibition of Chymotrypsin with Diisopropyl Phosphorofluoridate

IN a recent article Stein and Laidler 1 described the inhibition of chymotrypsin by di iso propyl phosphorofluoridate (DFP). They found that even when the inhibitor-enzyme ratio was as high as 4 : 1 no complete inhibition was observed. This was contrary to the results of Jansen et al. 2 , who found that when the molar ratio of DFP to enzyme was more than unity, there was practically 100 per cent inhibition.