332 



7. INHIBITION IN MULTIENZYME SYSTEMS 



and thus depends not only on F^/Fa but also on the concentration of the 

 initial substrate, A, and the Michaelis constant of E^. In the examples 

 plotted, (A) was assumed to be 1 milf ; if this were increased to 10 mM, 

 the buffer capacity would be increased 5.5-fold (from Fj/llFg to F1/2F2). 

 The relation between i^ and i in most multienzyme systems will not be 

 linear as it is here, and dildif will change with the degree of inhibition. The 



I on E2 



Fig. 7-7. Relationship between the over-all inhibition and the in- 

 hibition on E2 in a monolinear chain (Eq. 7-6). Curve 1: F1/F2 = 10; 

 curve 2: VJV^ = 3; curve 3: VJV^ = 1; curve 4: Fi/F^ = 0.33; 

 curve 5: V-^jV^ = 0.1. 



buffer capacity might also be defined as d{l)ldii, which is more comparable 

 to the definition of buffer capacity in acid-base systems, but it is felt that 

 dijdif defines better a property of the system and depends less on the 

 characteristics of the inhibition, thus being of greater value in comparing 

 different multienzyme systems. 



(B) Competitive inhibition. The response of the monolinear system to 

 competitive inhibition of E^ will be similar to that of the single enzyme 

 since (A) is assumed to remain constant. Competitive inhibition of E2, 

 however, introduces an additional factor because the rise in (B) will reduce 

 the inhibition on Eg. Inasmuch as competitive inhibition implies an in- 



