Il6 R. MAMELAK, J. H. QUASTEL VOL. 12 (1953) 



TABLE XIII 



EFFECTS OF THIOL COMPOUNDS ON LOSS OF ACTIVITY OF CI. SpOVOgemS DUE TO EXPOSURE 



TO AIR OR HYDROGEN PEROXIDE 



Warburg manometer vessels contained i ml CI. sporogenes suspension (in 0.15 M KCL), 0.028 M 

 NaHCOg. Gas 93% Ng + 7% COj- L-Alanine 0.005 ^^ • Glycine o.oi M. Time 135'. Temp. 37'^ Total 

 vol. 3.2 ml. Alanine tipped from side tube. 



Expt. Contents of vessel Conditions of exposure of ^iM CO, )":^^ £'>'""? 



•^ ■' CI. sporogenes evolved disappeared 



1 Alanine + Glycine + Thio- Freshly prepared organism used im- 



glycollate (0.012 M) mediately 12.5 25.5 



Alanine + Glycine Freshly prepared organism used im- 



mediately II. o 24.0 



Alanine + Glycine Organism exposed to air at 0° for 3 h 



before addition of amino acids i.o <i.o 



Alanine + Glycine Organism exposed to air at 0° for 3 h 



in presence of 0.12 M thioglycollate 

 before addition of amino acids 10.5 17.2 



2 Alanine + Glycine Freshly prepared organism used im- 



meditately 10.5 20.2 



Alanine + Glycine i ml organism diluted with 40 vols. 0.15 



+ Glutathione (0.005 ■^^) M KCl, centrifuged and resuspended 



in I ml 0.15 M KCl 11. 6 21.3 



Alanine + Glycine i ml organism diluted with 40 vols. 



+ Glutathione (0.005 M) 1/50,000 HjOj, centrifuged at once, 



resuspended in i ml 0.15 M KCl g.8 19.2 



Alanine + Glycine i ml organism diluted with 40 vols. 



1/50,000 HjOj, centrifuged at once, 



resuspended in i ml 0.15 M KCl 3.7 3.7 



Alanine -\- Glycine i ml organism diluted with 40 vols. 



+ Thioglycollate (0.005 -^^) 1/50,000 HgOj, centrifuged at once, 



resuspended in i ml 0.15 M KCl 10. o 17.6 



Exposure of CI. sporogenes to 1/50,000 hydrogen peroxide causes a large drop in 

 the rate of anaerobic amino acid interaction. If an organism, exposed in this way, is 

 washed free of hydrogen peroxide, and is now treated with amino acids in presence of 

 glutathione or thioglycollate, almost complete recovery of the rate of amino acid inter- 

 action takes place. These results show that the toxic effects of dilute hydrogen peroxide, 

 and presumably of oxygen, are reversed by subsequent exposure to thiol compounds, 

 and lead to the conclusion that the compounds affected by oxygen or hydrogen peroxide 

 have themselves a thiol constitution, and are possibly either thiol-enzymes or thiol 

 co-enzymes. 



Effects of organic arsenoxides on activities of CI. sporogenes 



The conclusion reached above that thiol compounds play a highly significant role 

 in the activities of CI. sporogenes is borne out by the extraordinary sensitivity of these 

 organisms to the presence of arsenoxides. As shown by Gordon and Quastel^*, phenyl- 

 arsenoxide or mapharside (m-amino-/)-hydroxy-phenylarsenoxide) is extremely reactive 

 with thiol enzymes (see also Singer^^). The presence of these substances, at low con- 

 centrations, greatly reduces anaerobic amino acid interactions, a concentration of 8 

 )Ltg/ml mapharside bringing about over 50% inhibition. Typical results are shown in 

 Table XIV. 



The amino acid reductase is much more vulnerable to attack by arsenoxide than the 



References p. 120. 



