INHIBITORS STRUCTURALLY RELATED TO MALONATE 



243 



Table 1-29 



Inhibitor Constants for Sulfonate, Phosphonate, and Arsonate Analogs of 



Substrates " 



" The A', values for rat and mouse liver succinate dehydrogenases were cal- 

 culated assuming A'^ = 6 X 10~^ M, and for beef heart succinate dehydrogenase 

 K^ = 4 X 10"* M. Although these values are undoubtedly inaccurate, the Aj values 

 so calculated are useful for comparisons since within each experiment the relative 

 values are reliable. 



rather poor inhibition produced by the arsono and phosphono derivatives 

 was postulated by Tietze and Klotz (1952) as possibly due to the extra 

 negative charge carried bj^ these substances. In the more recent work of 

 Rosen and Klotz (1957), the ionization was taken into account and the 

 inhibitor constants calculated on the basis of the concentration of doubly 

 charged anion present. Evidence that too high a charge reduces the inhib- 

 itory potency is provided by the falling off of the inhibition as the pH is 

 raised. On the other hand, it is difficult to understand why there should 



