118 



4. SUBSTEATE INHIBITION AND PRODUCT INHIBITION 



Inhibition by Attachment to Enzyme Groups Not Involved in the Active 



Complex (Type B) 



This situation presents no special problems since the substrate inter- 

 feres with the reaction in the same manner as the inhibitors discussed in 

 Chapter 3 and the appropriate equations may be obtained by substitution 

 of (S) for (I) in those equations and the replacement of K^ by yK^ if desi- 

 red (see Ijelow). An interesting formulation has been given by Friedenwald 

 and Maengwyn-Davies (1954, p. 180) and a similar, but somewhat more 

 general, treatment may be made assuming the following reaction scheme, 

 in accordance with Eq. 3-2: 



SE + P 



(4-8) 



where ES is the reactive complex and SE the complex that inhibits either 

 the formation or reactivity of ES. The rate equations for different types 

 of interference are: 



Completely competitive (a = oo): 



V = Vr, 



1 



1 + 1/(S') + 1/y 

 Partially competitive {co > a > \, fi = \): 



V = F™. 



1 



1 + a/(S') 



[(S') + y] 

 [(S') + ay] 



(4-9) 



(4-10) 



Completely noncompetitive (a = 1, /9 = 0): 



V = V 



1 



1 + 1/(S') + 1/y + (S')/y 

 Partially noncompetitive (a = l, 0<^<1): 



v = F. 



1 



(^/y) (S') 



Coupling (uncompetitive) {a = 0): 



V = F. 



1 + 1/(S') + 1/y + (S')/y 



1 



1 -h 1/(S') + (S')/ay 



(4-11) 



(4-12) 



(4-13) 



