584 



12. RATES OF INHIBITION 



continued to be released for several hours. The difficulty of interpretation 

 here lies in the fact, as mentioned above, that there are many different 

 sulfhydryl substances in the cell and their reactivity with iodoacetate varies 

 greatly. As a consequence, it is possible to assume that the course of gly- 

 colytic inhibition measures the reaction of iodoacetate with especially 

 susce]:)tible sulfhydryl groups on phosphoglyceraldehyde dehydrogenase 

 and that the bulk of the alkylation results from reaction wnth "nongly- 

 colytic" sulfhydryl groups. 



-400 



RELEASE OF IODIDE 



0.06 



0.04 <^ 



0.02 -f 



TIME (HOURS) 



Fig. 12-27. Release of iodide from iodoacetate in frog muscle and the rate of inhi- 

 bition of glycolysis. Iodoacetate was 1 niM and the temperature was 40°. (From 



Ghaffar, 1935.) 



The inhibition of glycolysis by iodoacetate in Streptobacterium casei 

 was studied by Field and Field (1932 a, b) and a definite latent period was 

 demonstrated; at 3.8 n\M iodoacetate, no inliil)ition was noted for 65 min, 

 and at 7.7 mM the latent period was reduced to 35 min. These results would 

 imply a permeability barrier of some importance in these cells. Once the 

 inhibition begins, the course is as shown in Fig. 12-28, wliich was inter- 

 preted as bimolecular but it could just as well be rejn-esentative of a 

 monomolecular reaction or a bimolecular reaction with one reactant in ex- 

 cess. Such a prolonged latent period followed by rather sudden development 



