PRODUCT INHIBITION 



141 



The quantity VpK„JV„,Kp = K^, the equihbrium constant for the over-all 

 reaction and is equivalent to (S)/(P). Thus one may write: 



V„ 



(S) - (P)ifo 



(4-38) 



(S) + K,[l + (P)/Z,] 



which is similar to the equation derived by Sturtevant (1954, p. 210). 

 When the equilibrium is far to the right, K^ will be very small and {^)Kq 

 may be neglected relative to (S): 



(S) 



V = F„ 



(4-39) 



(S) + K,[l ^ (P)/A%] 

 which is identical with the rate equation for competitive inhibition. Thus 



Fig. 4-16. Product inhibition by the reverse reaction. In the 

 upper graph A the rate is plotted against the product concen- 

 tration (Eq. 4-37) and in the lower graph B the fractional inhi- 

 bition is plotted against the product concentration (Eq. 4-40). 

 K, = 5 mM, Kj, = 10 mM, and (S,) = 10 mJ/. Curves I: 

 Vj>/Vm = 1; curves II: VJV^ = oo (Eq. 4-39). 



