178 T. VISWANATHA [10 



5-0 to 7-0, and, above pH 7-0, the rate is independent of pH. On the other 

 hand, in the case of E600 a sharp maximum for the reaction is noticed at 

 pH 6-90. The latter corresponds to the pH optimum for the reactivation of 

 E600 inhibited chymotrypsin reported by Cunningham.^ 



The difference in the behaviour of DFP and E600 recorded above might 

 be interpreted as suggesting the involvement of different groups on the 

 enzyme for the reaction with these organophosphorus esters. It might also 

 reflect on the inadequacy of any one amino acid side chain on the protein 

 molecule to account for the catalytic function of the enzyme. The enzymic 

 activity might be related to the presence of some special structure or spatial 

 configuration of groups in the protein molecule. 



A detailed report of this work will appear in Comptes rendus des Travaux 

 du Laboratoire Carlsberg, Série chimique. 



REFERENCES 



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3. J. R. WHiTAKER and B. T. JANDORF, /. Biol. Cliem., ll^y 751 (1956). 



4. T. WAONER-JAUREGG and B. E. HACKLEY, Jr., /. Atn. Cfiem. Soc, 75, 2125 

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5. G. H. DIXON, W. J. DREYER and H. NEURATH, /. Am. Chetti. Soc, 78, 4810 

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