126 



PHYSIOLOGICAL CHEMISTRY 



bases. The purine bases set free on the decomposition of nucleic acid 

 are adenine and guanine belonging to the class of amino purines. The 

 fate of the amino purines in the animal body is of considerable interest. 

 It has been shown that certain tissues contain enzymes which transform 

 these amino purines first to corresponding oxypurines known as hypo- 

 xanthine and xanthine and finally to uric acid. It is probable that differ- 

 ent enzymes enter into the various steps of these transformations lead- 

 ing to the formation of uric acid. Still another enzyme carries the oxi- 

 dation further with the formation of the compound allantoin. This 

 enzyme is known as uricase. The purine- enzymes are widely dis- 

 tributed in tissues. The transformations brought about are indicated 

 in the following diagrams. 



N=CNH 2 



i 



HC C NH 

 \ 



CH 



HN CO 



+H 2 O-NH,+ HC C NH 



\ 



Adenase 



N C N 



Adenine 

 6-amino purine 



CH 



N C N 



Hypoxanthine 

 6-oxypurine 



+0 



Hypoxanthine 

 oxidase 



HN CO 



HN CO 



I I 

 OC C NH 



H 2 N-C C NH 

 \ 

 CH +H 2 O-NH 3 + 



<y Guanase 



N C N HN C N 



Guanine Xanthine 



2-amino-6-oxypurine 2 -6-dioxy purine 



CH 



+0 



Xanthine 

 oxidase 



NH 5 



CO CO NH 0+H 2 O 



\ Uricase 



CO 



NH CH NH 



Allantoin 



HN CO 



I I 

 OC C NH 



\ 

 CO 



HN C NH 



Uric acid 

 2-6-8-trioxypurine 



