828 



15. EFFECTS OF VARIOUS FACTORS ON INHIBITION 



Table 15-5 

 Effects of NaCl on Erythrocyte Acetylcholinesterase 



" From Myers (1952 c). 



the activated complex for the breakdown of the ES complex is greater than 

 on the ES complex (see Eq. 15-90). 



Urease is very sensitive to changes in the ionic strength. Kistiakowsky 

 and Shaw (1953 b) worked with media containing no buffer and hence 

 were able to determine the effects of changes in the ionic strength in the 

 most sensitive range. These data fit the corrected Debye-Hiickel equation 



and the rate is inversely proportional to the square root of the ionic strengtli. 

 It makes very little difference what salt is used; NaCl, NaS04, KNOg, 

 and KBr all gave the same rate depression at comparable ionic strengths. 

 A dependence of the ionic strength effect on tlie pH was also demonstrated, 

 the depression of the rate by salts being greater at a pH of 8.95 than at 

 7-7.5. This is not surprising because the charges on the various components 

 and complexes in the enzyme reaction may be altered by the change in 

 pH. It was concluded that the effect of the ionic strength was mainly on 

 Jc^ since it was independent of the substrate concentration. 



The addition of either NaCl or KCl to cc-chymotrypsin leads to an in- 

 crease in the rate of hydrolysis of chloroacetyl-L-tyrosinamide and the 

 effect is primarily on k.^ with little if any change in K^. The results can be 



