CHAPTER LXXIV 



URIC ACID AND THE PURINE BODIES 



Introductory. The participation by highly trained organic chemists 

 in the investigation of biochemical problems has brought our knowledge 

 of the history of the purine substances in the animal body from a state 

 of chaos and guesswork to one of system and scientific accuracy. The 

 peculiar solubility reactions of uric acid and its salts and the discovery 

 of urates in gouty deposits served to make uric acid metabolism one of 

 the earliest research problems in both the medical clinic and the bio- 

 chemical laboratory, but the earlier results were practically valueless, 

 partly because they were inaccurate and partly because their interpretation 

 was impossible in the absence of even the most elementary facts concerning 

 the chemistry of uric acid. 



Before any real progress was possible, a clean sweep had to be made 

 of all the old speculations and hypotheses, such as that dignified by the 

 high-sounding name of " uric-acid diathesis," and a foundation of ac- 

 curate chemical knowledge established. This foundation is now wonder- 

 fully complete, and a superstructure of biochemical fact is already 

 beginning to grow upon it. In the present chapter we shall examine 

 some of the most important contributions that have made this progress 

 possible, 



As in the study of any other problem of metabolism, we must, however, 

 make ourselves familiar with the main facts concerning the chemistry 

 of the purine bodies and of the tissue constituents into the composition 

 of which they enter, before proceeding to the more strictly biological 

 aspect of the subject. 



The Chemical Nature of the Purines 



By an examination of the empirical formulas of the purines of biochemical interest, 

 it will be observed that they are all derivatives of a substance purine, which although 

 in itself of no importance is interesting, since it serves as the basic substance from 

 which the others are derived. The list is as follows: 



Purine . C 6 H 4 N 4 



Hypoxanthine C 5 H 4 N 4 O Monoxypurine f 



Adenine . C 5 H 3 N 4 .NH 2 Ammo-purine I Purine 



Xanthine . C 5 H 4 N 4 O 2 Dioxypurine 1 bases. 



Guanine . C 5 H 3 N 4 O.NH 2 Amino-oxypurine 1 ' 



Uric acid . C 5 H 4 N 4 O 3 Trioxypurine 



The first oxidation product of purine is hypoxanthine, which has long been known 

 as a constituent of meat extract. Adenine, the amino derivative qf hypoxanthine, 



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