DAVID NACHMANSOHN AND IRWIN B. WILSON 



or diethylfluorophosphate inhibition hydrolyzes in a few days, 

 as evidenced by the return of enzyme activity (35), 



Since it was apparent that reactivation would require the 

 dephosphorylation of the inhibited enzyme, reactivating agents 

 were sought amongst nucleophilic reagents and a large number 

 of compounds such as hydroxylamine, pyridine, imidazole, es- 

 ters and amides of amino acids, amidines, guanidines, oximes, 

 hydroxamic acids, and choline were found to be active in 

 periods of time varying from one minute to several hours 

 (35,37,39,47-49). 



u/ - Vi M i-y G loj 

 / I 



Fig. 3. Promotion of reactivation of alkylphosphate in- 

 hibited enzyme by anionic site. Attack of the reactivator (nico- 

 tinohydroxamic acid methiodide) upon phosphoryl group is 

 aided by Coulombic attraction. 



Since an alcohol group could hardly be considered a strong 

 nucleophilic function, it appeared that choline was active largely 

 because its intrinsic activity could be promoted by interaction of 

 the quaternary ammonium structure with the anionic site. 

 The anionic site, it might be noted, is only indirectly affected by 

 the inhibition. It has been possible in many instances such as 

 illustrated by nicotinohydroxamic acid and its methiodide to 

 increase the activity of a reactivator by introducing a cationic 

 center in the molecule (Figure 3) , and in all cases of reactivators 

 containing a cationic center it has been possible to demonstrate 

 a marked promotion by the anionic site (Wilson (40)). What 

 is the nature of this promotion? There is clearly to be expected 

 a general enhancement resulting from the Coulombic attraction 

 of oppositely charged reactants, but is there evidence for a more 

 specij&c type of interaction? The fact that dimethylamino- 

 ethanol ammonium ion is very much poorer than choline would 



640 



