REGENERATIVE SYSTEMS 



361 



to inhibition of E^ or Eg. When the first term in the coefficient is much 

 greater than the second, the steady-state rate will be more sensitive to in- 

 hibition of E2, and when it is much less than the second term, the rate will 

 be more sensitive to inhibition of E^. Figures 7-32 and 7-33 show the effects 

 of inhibition in a system where the second term is greater than the first, 

 i.e., where the second reaction is potentially faster than the first, and a 

 marked degree of buffer capacity is observed when Eg is inhibited, espe- 



FiG. 7-27. Noncompetitive inhibition of E3 in the cychc system shown 

 in Fig. 7-16. (M), = 1 mM. 



cially when the concentration of the regenerated coupler B is high. Regen- 

 erative reactions thus have the important property of being particularly 

 sensitive to inhibition on that enzyme which is potentially the slowest, 

 this being determined by the relative values of the constants i?,„ and k 

 and the concentration of enzyme (E^). The reason for this characteristic 

 behavior is the constancy of (B),. When Eg is inhibited, (BX) rises, but 

 this requires a necessary reduction in (B) so that the first reaction is slowed, 

 the degree of slowing being dependent on the change brought about in 

 the ratio (BX)/(B)^. 



