360 



7. INHIBITION IN MULTIENZYME SYSTEMS 



[(B), + A^ + A',,] [(AX) + AJ [(C) + A,] u%, 

 - {Fi(AX)[(B), + A,.][(C) + A,] + F,(C)[(B), + A,][(AX) + K,,])v,, 

 + (B),(AX)(C) FiF, =0 (7-45) 



The nature of this quadratic equation is such that v,^ will always have a 

 real and physically compatible value whatever the concentrations or con- 

 stants. It also illustrates that the steady-state rate is dependent on both 

 reactions and not only on the first. From this equation the value of v^i 

 may be determined for any assumed system and its changes calculated 

 when the concentrations are altered or inhibition is imposed. 



Fig. 7-26. Noncompetitive inhibition of E3 in the cychc system shown 

 in Fig. 7-16. (M), = 0.1 mi/. 



Inhibition of Regenerative Systems 



The steady-state rate of a regenerative system may be more sensitive 

 to inhibition of either E^ or E,. depending upon the initial uninhibited state 

 of the system. Inspection of Eq. 7-45 shows that when the two terms in 

 the coefficient of v^t are equal, identical reductions of either V^ or Fg 

 will have the same effect on v,/, such a system would be equally sensitive 



