RESPIRATORY METABOLISM 381 



in which glutathione is not present. ) Therefore we may use it as an ad- 

 ditional indicator in detecting the action of glutathione in respiration. 

 M. Lwoff found that monoiodoacetic acid produced 61-82 percent in- 

 hibition of respiration of Glaucoma in concentrations of one part in 

 121,000 to 77,000, while the cihates appeared normal and moved slowly. 

 These results are interpreted to indicate that glutathione seems to be 

 quite important in the respiration of Glaucoma. Another interpretation 

 which has been used for work on other material (Korr, 1935; Cohen and 

 Gerard, 1937) is that arsenites inhibit dehydrogenases (Szent-Gyorgyi 

 and Banga, 1933). It is interesting that the accepted dehydrogenase in- 

 hibitors (urethanes, see below) do not result in as great an inhibition 

 with Glaucoma as arsenites and monoiodoacetic acid. 



Another respiratory mechanism which might exist among the cyanide- 

 insensitive Protozoa is the yellow pigment found in yeast and other an- 

 aerobic organisms. It seems as if an investigation of the distribution of 

 enzyrnes of this type should be made among the Protozoa, especially with 

 those species in which respiration proves to be cyanide insensitive. Since 

 a large number of Protozoa are presumably facultative anaerobes, it 

 might be possible to poison the normal aerobic mechanism and study the 

 anaerobic mechanisms under various conditions, as has been done for 

 Escherichia coli by Broh-Kahn and Mirsky (1938). 



4. INHIBITION OF THE DEHYDROGENASE SYSTEM 



The dehydrogenases are apparently a part of the respiratory chain in- 

 volved in several of the enzyme mechanisms. Therefore one would ex- 

 pect any substance which inhibits the dehydrogenases to inhibit 

 respiration. Such is the case with the urethanes. M. Lwoif (1934) found 

 that in the respiration of Glaucoma one percent methyl urethane pro- 

 duced 9 percent inhibition of respiration, 2 percent inhibited 38 percent, 

 2.5 percent inhibited 52 percent, and 3.5 percent inhibited 55-63 percent. 

 Ethylurethane in concentration of 1.66 percent inhibited 44 percent, and 

 2 percent inhibited 57-61 percent. Propylurethane in 0.5 percent solu- 

 tion produced an inhibition of 47 percent. The ciliates appeared normal, 

 movement was slow, but the effect on respiration was reversible. There- 

 fore we may conclude that dehydrogenase systems are probably involved 

 in the respiration of Glaucoma. It might be interesting to try the com- 

 bined effects of urethane and arsenious acid, in order to obtain evidence 



