THE METABOLISM IN GOUT 413 



From these two reactions it is evident that purin must contain the 

 rings of the pyrimidin nucleus and of the imidazol nucleus which when 

 condensed form purin. 



Purin is related to substances like cytosin and uracil, because of its 

 pyrimidin group, and to histidin, a constituent of protein, because of its 

 imidazol group. 



The ^alloxuric bases," hypoxanthin, xanthin, adenin and guanin (all 

 discovered by Kossel) were shown by him to form the only source of uric 

 acid. 



The investigations of Fischer made clear the relation of the purin bases 

 to each other and to uric acid. The simplest member of the group is 

 the hydrogen compound, purin (C 5 II 4 lsr 4 ) made up of the purin nu- 

 cleus plus four atoms of hydrogen. This is not found free in nature. 

 The addition of oxygen to purin causes the formation of hypoxanthin, 

 xanthin and uric acid. If an atom of hydrogen is replaced by amid (NH 2 ) 

 adenin is formed. If in addition there enters an atom of oxygen guanin 

 results. Methyl groups join the nitrogen atoms and form methyl purins, 

 theobromin, theophyllin and caffein. 



In the formulas given below the situation in the purin ring of the atoms 

 added is indicated by the number given by Fischer. 



CO 



Hypoxanthin (C 5 H 4 N 4 O) = 6 Oxypurin = HC C 



II ) H 



C -N 



-CO 



Xanthin (C 5 H 4 N 4 O 2 ) = 2.6 Dioxypurin = CO C NH 



| || > CH 



HN C N 



HN CO 



Uric acid (C 5 H 4 N 4 O 3 ) = 2.6.8 Trioxypurin = CO C KH 



I I > CO 



C 



Adenin (C 5 H 5 N 5 ) = 6 Aminopurin = HC C NH 



H I \PTT 



i| ^ CH 



N C IT 



