764 



15, EFFECTS OF VARIOUS FACTORS ON INHIBITION 



When either K is very large or K, = K- , the inhibition becomes purely 

 noncompetitive, but generally is dependent on the substrate concentration 

 in a complex fashion. The variation of the inhibition with temperature will 

 depend on the ratio of KJK/. 



The variation of the inhibition with the temperature in such systems 

 will thus depend on the form of the enzyme with which the inhibitor com- 

 bines and whether the inhibition is competitive of noncompetitive. Of course, 

 other types of inhibition, such as uncompetitive or coupling, may occur. 

 The change in inhibition with K for case V has been plotted in Fig. 15-5 



08- 



0.6- 



04 - 



0.2 



Fig. 15-5. Variation of the inhibition with K, the equihbrium 

 constant between active and inactive enzyme, for case V where 

 the inhibitor combines with both E^, and E^ noncompetitively 

 (scheme 15-30 and Eq. 15-32). (I) = 1 miJf , (S) = 1 mM, Ki = 1 

 mM, and K^ = 1 vaM. The figures on the curves are values 

 of the ratio KJK/ . 



and it may be observed that when K is high, the inhibition approaches 50% 

 whatever the ratio KJK/ for the specific situation selected. If increasing 

 the temperature brings about a shift in the equilibrium to form more of 

 the inactive enzyme, i.e., K becomes smaller, the inhibition will either in- 

 crease or decrease depending on whether the ratio KJK/ is greater than 



