IRREVERSIBLE MONOLINEAR CHAINS 



325 



be constant because (B) is probably increasing with time. The results of 

 inhibition on such systems will depend on whether the system is in a 

 steady or nonsteady state. 



Graphical Representation of Sequential Reaction Chains 



It is convenient to visualize the relationships in multienzyme systems 

 by inspection of the rate curves for each enzyme reaction involved. Such 

 curves are plotted for three values of Fj/Fg in Figs. 7-2, 3, and 4. When 



(S) 



lOOOmM 



Fig. 7-2. Rate curves for a monolinear chain. Curve Vi shows the rate for reaction 1 

 alone: Vi — 3 and K^ = 10 mM. Curve Uj shows the rate for reaction 2 alone: Fg = 1 

 and K2 = 2 mil/. Curve t'2' shows the rate for reaction 2 alone: V^ = I and K^' = 0.5 

 mil. Dashed lines cut the curves V2 and Vj' at points indicating the concentration of 

 B necessary for the steady state when (A) = 3 mM. 



F1/F2 = 3 it is seen that if i'^ is greater than Fg the system cannot be in 

 a steady state, for B cannot be reacted at a rate faster than Fg whatever 

 (B). In the present case, this puts a limit on (A) of 5 mM for a steady state. 

 When F1/F2 = 1 or 0.33 the system can always be in a steady state at any 

 value of (A), since v\ can never be greater than Fg, but restrictions may limit 

 the level that (B) can attain and hence there may be a maximal (A) beyond 

 which the steady state will not occur. 



From these curves the value of (B) for any substrate concentration can 

 be estimated wlien the system is in a steady state. A horizontal line is 

 drawn at the rate of reaction 1 for the specified concentration of A and 

 the intersection with the rate curve for reaction 2 gives (B). Thus in the 



