330 



7. INHIBITION IN MULTIENZYME SYSTEMS 



Inhibition of E2 will increase (B) and the rate of formation of C will 

 not be reduced as long as the system can remain in a steady state. It is 

 evident that if Fg is decreased below v^, the steady state cannot be main- 

 tained and the formation of C will be depressed. The rise in (B) upon inhi- 

 bition depends on the relative maximal rates of the two reactions (V1/F2) 

 as shown in Fig. 7-6. When the system is barely in the steady state, as in 



Fig. 7-6. Curves showing the rise in (B) following inhibition of Eg 

 in a monolinear chain. K^ = 10 mil/, K2 — 2 mM, and (A) = 1 mM. 

 The numbered lines on the i axis show the maximal inhibitions 

 which may be exerted before the systems leave the steady state. 

 See Eq. 7-4. Curve 1: VJV, ^ 10; curve 2: Vj/V^ = 3; curve 3: 

 VJV^ = I; curve 4: VJV^ = 0.33; curve 5: VJV^ = 0.1. 



curve 1 where V1IV2 = 10, it requires very little inhibition to increase 

 (B) and take the system out of the steady state; in fact, for the system 

 plotted, only 9% inhil^ition will make the steady state impossible. Of 

 course, the high values of (B) necessary for the steady state may not be 

 able to be achieved and the system will leave the steady state sooner. As 

 the maximal rate of reaction 2 becomes greater relative to reaction 1, it 

 requires more and more inhibition to increase (B). An expression for the 

 change in (B) may be derived as follows. If it is assumed that the maximal 



