INHIBITOR AS SUBSTRATE FOR THE ENZYME 



97 



substrate reaction by reducing the available substrate sites. However, if 

 both reactions are determined together (e.g., when the products measured 

 are identical for each reaction or both products absorb similarly in a spectro- 



FiG. 3-20. Variation of the fractional inhibition with varying 



interaction of two adjacent active centers (Eq. 3-94). Ki — O.l mM 



and (I) = 0.1 raJ/. 



photometric determination) the inhibition is more complex. The reactions 

 to be considered are: 



E+S^ES^E+P, (3-96) 



E + I ^ EI -4 E + P, 



(3-97) 



The over-all rate is the sum of the individual rates when both substrate 

 and inhibitor are present: 



F,(S') + VAl') 



'' = '^ -^'^ 1+ (S') + (D 

 and the inhibition relative to the rate with substrate alone is: 



(P) 



(P) + 1 + (S') 



1 



F 



pXs 





(3-98) 



(3-99) 



