94 



THE CHEMICAL COMPOSITION OF THE BODY 



Three derivatives of pyrimidine, cytosin, uracil, and thy mine, were obtained 



These derivatives have all 



by Kossel and his co-workers from nucleic acids, 

 been prepared synthetically. 



N=C-NH 2 HN-C=0 



0=C CH 0=C CH 



HN-CH HN-CH 



Cytosine. Uracil. 



(2-oxy- 6-amino pyrimidine.) (2-6-dioxypyrimidine.) 



HN-C=0 



o-A L 



CH 3 



HN-CH 



Thymine. 



(2-6-dioxy- 5-methyl- 

 pyrimidine.) 



Purines. To the purines belong a number of extremely important animal 

 and plant substances, including adenine, guanine, hypoxanthine, xanthine, 

 and uric acid, and the methyl purines caffeine, theobromine, and theophylline. 



The mother substance of the purines is known as purine, which has the 

 following structure : 



'N-C 6 



2 C C 5 -N\ 



I ! >c 8 



3 N-C 4 -N 9 / 

 Purine ring. 



N = CH 

 HC C-NH 



iCH 



N-C-N 

 Purine. 



Adenine and guanine may be converted into hypoxanthine and xanthine, 

 respectively, when added to extracts of tissues, such as the liver and the thymus, 

 spleen and pancreatic glands. The "deamidization" is brought about by 

 specific enzymes or non-living ferments which have been termed adenase and 

 guanase. On slight oxidation, hypoxanthine is converted into xanthine, and 

 the latter into uric acid. This change can also be brought about in the body 

 by oxidizing enzymes. The relation of the purine bases to uric acid is indicated 

 in the following scheme: 



on oxi- 



dation 



HN-C=O 



+ H 2 



H 2 N-C C-NH ; 0=C C-NH 



-NH, 



>CH >CH 



N-C-N HN-C-N 



Guanine. Xanthine. 



(2-amino 6-oxypurine.) (2-6di-oxypurine.) 



HN-C=O HN-C=O 



on oxidation 



> 0=C C-NH 



- 



HN-C-NH 



Uric acid. 

 ( 2-6-8-trioxypurine.) 



