340 



7. INHIBITION IN MULTIENZYME SYSTEMS 



to inhibition will be essentially the same as in system 7-13. In these con- 

 nections it must be remembered that noncompetitive inhibition of a re- 

 versible step implies equal inhibitions on both the forward and the reverse 

 reactions (see Chapter 3 under system 3-105). However, competitive in- 

 hibition is not necessarily the same on the rates in forward and reverse 

 directions and some complication is introduced into the quantitative re- 

 sponse to such inhibition. 



0.4 



0.3- 



02 



0.1 



^st 



2.0 



- 1.6 



- 1.2 



-0.8 



-04 



(8) 



Fig. 7-12. Noncompetitive inhibition of Ej in a partially reversible monolinear chain. 



Fi = 3, F_i = 1, K^ = 10 ml/, K^ = 2 mM, K_^ = 20 mM, and (A) = 1 mM. 



The dashed curve shows the change in v^i in an irreversible system. 



BRANCHED LINEAR CHAINS 



Branched chains may be of two general types: (1) convergent where two 

 or more substrate systems feed into the chain, or (2) divergent where two 

 or more products are produced by a monolinear chain. 



Convergent Chains 



Many examples of convergent enzyme sequences in metabolism have 

 been reported: the formation of glucose-6-phosphate from both glucose 



