188 



1. lODOACETATE AND lODOACETAMIDE 



Table 1-32" 



Effects of Iodoacetate and Various Cycle Intermediates on Bromide 

 Accumulation and Respiration of Barley Roots 



" From Machlis (1944). 



ence of 10 mM iodoacetate increases it from 1.69 to 2.57 (Guroff et al., 

 1961). If anything, this indicates that the primary action of iodoacetate is 

 on the cycle, inasmuch as glucose should not overcome a block of 3-phos- 

 phoglyceraldehyde dehydrogenase. On the other hand, possibly glucose 

 plays a role in tyrosine uptake before the iodoacetate block. Another unex- 

 pected observation is that arsenate, although having no effect by itself, 

 counteracts the loss of K+ induced by iodoacetate in Ulva (Scott and Hay- 

 ward, 1954); perhaps arsenate stimulates the formation of pyruvate through 

 a partial iodoacetate block and allows more energy to be derived from the 

 cycle. 



Effects of Light on Transport Inhibition in Photosynthetic Organisms 



Iodoacetate causes a marked fall in cell K+ and comparable gain in Na+ 

 in Ulva in the dark (Scott and Hayward, 1953). However, in the light iodo- 

 acetate has no effect on K+, even at concentrations higher than those cans- 



