Is Cystin Synthesized in the Animal Body? 47 



In 1879 Baumann 4 and Jaffe 5 independently discovered that 

 brom-benzene fed to dogs is detoxicated by joining the cystein 

 molecule followed by an acetylation of the amino group of the 

 latter. 



We thought that perhaps under these conditions of brom- 

 benzene intoxication it might be possible for the organism to 

 synthesize cystein, although it was unable to do so for dietary 

 purposes. 



Kopf hammer 6 at this time published a paper showing that on 

 a non-protein diet the dog is unable to synthesize cystein, al- 

 though at the same time fed brom-benzene. We then undertook 

 three series of experiments. In the first we placed the dog on a 

 carbohydrate diet and fed each day brom-benzene. Besides this 

 on the first two days we fed sodium sulphate, the second two 

 days we fed taurine, the next two days calcium sulfate, the fol- 

 lowing two days sodium sulphocyanate, then following this 

 ethylamino mercaptan, and finally cystin. Thus the dog was 

 furnished more than sufficient sulphur in many different forms 

 but was unable to use it for the elaboration of cystein. Only 

 when cystin was fed was there a detoxication of brom-benzene 

 in the manner described above. The second experiment was a 

 repetition of the first but added to this was sufficient ammonium 

 acetate to furnish inorganic nitrogen for the amino group of 

 cystein, but still no synthesis of this amino acid. The same re- 

 sults were obtained in a third experiment which was a repetition 

 of the second, only gelatine was added to furnish the organic 

 nitrogen instead of the inorganic nitrogen. 



It is safe to say therefore that cystein and consequently cystin 

 can not be synthesized in the animal body even under the strain 

 of brom-benzene poisoning when inorganic or organic nitrogen 

 is furnished for the amino nitrogen and different forms of 

 sulphur for the sulphydril group. 



4 Baumann, E. and Preusse, C, Ber. chem. Gesellsch., 1879, xii, 806. 



5 Jaff£, M., Ber. chem. Gesellsch, 1879, xii, 1092. 



• Kopf hammer, J., Zeit. Physiol. Chem., 1921, exvi, 302. 



