SPECIFIC TYPES OF INHIBITION 



177 



llv axis 1/F,,,. The general characteristics of the standard plots are shown in 

 Fig. 5-17. The meaning of a or the calculated inhibition constant will vary 

 with the choice of binding situation or mechanism; it usually is not the 

 dissociation constant of the ES^Sa complex into ES^ and S.,. 



Fig. 5-17. Substrate inhibition of type A. The dotted Hnes represent the uninhi- 

 bited reaction. See Eq. -4-7. 



Inhibition of enzyme systems in which substrate inhibition occurs does 

 not present serious problems as long as the substrate inhibition is recognized 

 and the proper graphical methods are used. Figures 5-18 and 5-19 give the 

 plots for noncompetitive and competitive inhibition in such systems and 

 the characteristics of those graphs involving (S) are dominated by the 

 substrate inhibition; in fact, for noncompetitive inhibition, where the 

 degree of inhibition doesn't depend on (S). the curves are merety raised or 

 lowered a constant fraction at any inhibitor concentration. The plots of 

 types E and F are the most valuable here and the inhibition constant may 

 be obtained directly. 



