XUCLE1C ACIDS 157 



ferments are seldom associated with one another, it seems queer that they 

 should ever have been thought identical. 



Muscular hypoxanthine, which forms a considerable part of what 

 Burian and Schur call "endogenous" uric acid, is not the result of the 

 action of adonase on adenine. Leonard and Jones were not able to observe 

 a transformation of adenine into hypoxanthine by aqueous extracts of 

 muscle, while Voegtlin and Jones found that perfused adenine is not 

 altered by surviving muscle. 



But the path of adenine metabolism does not always pass through hypo- 

 xanthine. None of the organs of the rat exhibit adenase (Rohde and 

 Jones), and Nicolaier found that in rats subcutaneously injected adenine 

 is oxidized but reaches the kidney without deaminization where it forms 

 concretions of G-amino-2-8-dioxypurine. 



/H /OH 



P NH 2 + 20 = P NH 2 

 \H \OH 



adenine 6-amino-2-S-dioxy-piirine 



Ebstein and Bendix found a similar transformation of adenine in 

 the organism of the rabbit. But these two are the only authentic cases 

 in the literature where oxidation of a free amino-purine was found to oc- 

 cur without deaminization. 



8. The distribution of the purine ferments is often obscure, because 

 a given tissue extract may be able to bring about the decompositian of a 

 combined pairine but unable to effect a similar decomposition of the free 

 base. Thus, dog's liver cannot convert free adenine into hypoxanthine, 

 but it can form hypoxanthine from nucleic acid with the greatest ease. 

 Human tissues do not contain adenase, yet the subcutaneous injection 

 of adehosine causes a marked increase of uric acid. (Thannhauser and 

 Bornmes.) 



A purine base may even undergo both deaminization and oxidation 

 while still combined. Benedict (a) (1015) has shown that about 00 per 

 cent of the uric acid of ox blood is in combined form. It is present only in 

 the corpuscle and is set free by a ferment present when the blood is allowed 

 to stand. This contrasts sharply with the uric acid of chickens' blood, 

 which does not have a purine precursor. Here the uric acid is all free 

 and in the plasma. 



Bass found that the purine bases of human blood are combined, and 

 can only be detected after acid hydrolysis. He was able to isolate adenine 

 but at most only traces of guanine. 



9. The purine metabolism does not always suggest evolutionary rela- 

 tions, but it often does. The proof that uricase is not present in the 

 tissue extracts of either the ape or man, and that allantoine is not present 

 in the urine of either species (Wiechowski (e)), surely justifies all the 



