364 



7. INHIBITION IN MULTIENZYME SYSTEMS 



Regenerative Systems of Greater Complexity 



In some cases the coupling is not as close as in scheme 7-39 and two or 

 more reactions may be interposed before regeneration of the intermediate 

 is achieved. An oxidation-reduction system involving hydrogen transfer 

 may utilize some metabolic product of the substrate for regeneration: 



El 



AHj + Co -> A -f- CoHj 



A -» B 



E3 

 B + C0H2 -> BH2 + Co 



(7-46) 



AH, 



BH, 



Fig. 7-32. Effect of noncompetitive inhibition of Eg on the ratio 



(BX)/(B)^ in a regenerative system (7-39). Curve 1: (B)^ = 0.1 mM; 



curve 2: (B)^ = 10 mJf . 



Co is a coenzyme which transfers hydrogen atoms and is regenerated. The 

 anaerobic formation of lactate by the glycolytic pathway occurs in this 

 way: AHg is glyceraldehyde-3-phosphate, B is pyruvate, and Co is DPN+, 

 omitting the phosphorylation. In this case the reaction A -^ B is not a 



