78 



ENZYMES AND DRUG ACTION 



arsenoglyceric acid decomposes spontaneously, so that no 

 diphosphoglyceric acid is available as substrate for the 

 next enzyme in the series. 



Problems in the Analysis of the Action of 

 Drugs on Enzymes 



When a drug is acting upon a simple solution of an en- 

 zyme, the analysis of the effect of the drug may be 

 relatively simple. For example, when the percentage 

 inhibition of an enzyme is plotted against the logarithm 

 of the concentration of the inhibiting drug, a linear curve 

 is quite commonly obtained. When drugs are acting 



200 



-100 



-4 -3 -2 



log concentration of phenol 



Fig. 12. The respiration of yeast (a) and the fermentation of sugar by 



yeast (b) as affected by phenol 



upon cells, the action-concentrations curves are some- 

 times linear, sometimes non-linear. And even when they 

 are linear it does not follow necessarily that the action 



