FORMATION OF URIC ACID 143' 



associated with the breaking up of protein into amino-acids 

 reduces their available energy but little. This too, most 

 likely, is true of the separation of the nitrogen from amino- 

 acids, leaving thus a residue rich in carbon, with almost the 

 same potential energy as the original protein. Finally, it may 

 be said that under the influence of a special uricolytic enzyme 

 a part of the uric acid (one-half in man) may be converted to 

 urea. 



Formation of Uric Acid. This waste product, like urea, 

 is separated from the blood by the kidney. It is remarkably 

 increased in gouty persons. There can be no doubt that in 

 birds uric acid is the result, mainly, of a synthetic process 

 in the liver. A similar but less pronounced process takes 

 place in the liver of mammals, but the main source of uric 

 acid lies in the breaking up and oxidation of nucleins, taking 

 place in all the tissues of the body. A second source lies in the 

 taking of food rich in nucleoprotein, or rich in purin bases, 

 like Liebig's meat extract. When nucleoprotein is digested 

 with gastric juice some protein is easily split off and yields 

 the ordinary products of proteolysis. The insoluble residue 

 is nuclein. The latter may be easily hydrolyzed by heating 

 with dilute hydrochloric acid which yields another protein 

 and nucleic acid. In order to break up nucleic acids it is 

 necessary to heat in a sealed tube with hydrochloric acid. 

 As a result, phosphoric acid, purin bases, and often, but not 

 always, pyrimidin bases appear. Knowing the above, it is 

 not difficult to formulate the manner in which uric acid results 

 from the breaking up of nucleoproteins. 



There are organs which contain ferments which split nucleo- 

 proteins. The resulting nucleins, together with those derived 

 from the digestive tract, are decomposed by another ferment, 

 nuclease, yielding phosphoric acid, a carbohydrate group, 

 pyrimidin and purin bases. Among the latter are adenin and 

 guanin. The ferments, adenase and guanase, remove the amino 

 group from these purin bases, transforming adenin into hypo- 

 xanthin and guanin into xanthin. Now, by means of the 

 ferment oxydase, hypoxanthin is oxidized to xanthin and 

 xanthin to uric acid. The uric acid which comes from the food 

 is distinguished as exogenous, from the endogenous portion 

 derived from the tissues. The latter amounts to 0.6 gram 



