INHIBITION OF ENZYMES 



863 



strongly dependent on several factors, such as pH, temperature, and me- 

 dium composition, so that these conditions should be stated accurately 

 and completely, and it should always be realized that the results reported 

 apply only to these particular conditions. 



Fig. 7-31. Inhibitions of glutamate dehydro- 

 genase, showing the relative potencies of the 

 various inhibitors. Glutamate =11 mM, NAD 

 = 0.17 mM, and pH 7.6. (From Olson and 

 Anfinsen, 1953.) 



Inhibition of ATPase 



The results of the actions of the mercurials on ATPase were not included 

 in Table 7-13 because they are complex and warrant more detailed treat- 

 ment, particularly as the effects of mercurials on mitochondrial and myosin 

 ATPase are of importance in the work on oxidative phosphorylation and 

 muscle contraction, respectively. Some of the reported inhibitions of ATPase 

 are shown in Table 7-14; the stimulation of ATPase under certain conditions 

 has been omitted since it was presented in Table 7-11. One immediately 

 notes a very great variation in results. This is due partly to the different 

 sources of the enzyme, but also to the different conditions under which 

 the experiments were run. The response to mercurials depends on the state 

 of activation of the enzyme, whether Ca++ or Mg++ is present, the pH, and 

 the temperature, as well as the obvious factors of buffers and nonenzymic 

 protein. The pH actually determines whether stimulation or inhibition will 



