138 1. lODOACETATE AND lODOACETAMIDE 



is also depressed. The patterns of aerobic glucose metabolism in yeast as 

 affected by iodoacetate are well seen in the accompanying tabulation. The 



decrease in total glucose utilized is due mainly to the reduction in the frac- 

 tion anabolized, which is rather surprising and hardly explainable entirely 

 on the basis of an action exclusively on 3-PGDH. In brain slices the situa- 

 tion is somewhat different, in that 0.03 mM iodoacetate inhibits glucose 

 utilization 19%, glucose oxidized (calculated) 28%, lactate formed 9%, and 

 respiration 4% (Takagaki et ah, 1958). In ox retina the reduction in glu- 

 cose utilization by iodoacetate is also probably due mainly to the inhibi- 

 tion of the EM pathway and the fraction of glucose being oxidized or going 

 to lactate (Hopkinson and Kerly, 1959). Since in some cells (e.g. ascites 

 cells) glucose inhibits the respiration (Crab tree effect), the effect of iodoace- 

 tate is particularly interesting. Would iodoacetate stimulate the respiration 

 from its glucose-depressed level by blocking its metabolism? Ibsen et al. 

 (1958) state that it does not, although their results indicate that slight 

 stimulation may possibly occur with low iodoacetate concentrations. How- 

 ever, iodoacetate reduces the Crabtree effect, as also reported by Laws and 

 Stickland (1962). Quite other results were obtained by Wu and Racker 

 (1959), who found the Crabtree effect to be even greater in the presence of 

 iodoacetate (see accompanying tabulation), which means that iodoacetate 



