374 



7. INHIBITION IN MULTIENZYME SYSTEMS 



obtained in terms of (B)i by equating 7-58 and 7-59 and solving for {B)^, 

 leading to the quadratic equation: 



(B)! 



D 



+ K, 



(B)i 



(B), - A',(B), = 



(7-60) 



From (B)2 the steady-state rate of the reaction may be calculated. Inspection 

 of Eq. 7-60 shows that the greater the distance between the planes, the 

 less (B)2 will be and the slower the reaction rate will be. Also the greater 

 the diffusion coefficient, the higher (6)2 will be and the more rapid the 

 reaction rate; thus, in the general case, the rate of formation of C will be 

 dependent upon the diffusion process, both with respect to the rate of 

 diffusion of B and the distance to the reactive sites. Of course, when ^^ — 

 (B)i is much larger than VidjD, changes in either d or D will not alter {B)2 



Fig. 7-37. Diagram illustrating diffusion 

 of substance, B, from plane 1 to catalyt- 

 ic plane 2 where it is reacted to form C. 



or the rate appreciably. If the enzyme is inhibited, (B)2 will rise in the 

 general situation and counteract the inhibition to maintain the steady rate 

 within limits; however, in almost all cases there will be some inhibition on 

 the rate of formation of C, although generally less than on the enzyme in the 

 presence of constant substrate concentration. When V^jdlD is small com- 

 pared to jfiTj — (B)i, that is, when the enzyme rate is inherently slow, the 

 distance is small, or the diffusion is rapid, inhibition of the enzyme will 

 produce identical inhibition in the formation of C; these would be conditions 

 in which diffusion is not limiting and (B)2 is approximately equal to (B)i. 



