PURINE BASES. 183 



cells appear in such places as were before relatively poorly endowed. 

 As an example of this, the blood, in leucaemia, is extremely rich in leu- 

 cocytes. In such blood KOSSEL 1 found 1.04 p. m. purine bases, against 

 only traces in the normal blood. That these bases are also intermediate 

 steps in the formation of uric acid in the animal organism is probable, 

 and will be shown later (see Chapter XV). 



Only a few of the purine bases have been found in the urine or in the 

 muscles. Only four bases xanthine, guanine, hypoxanthine, and ade- 

 nine have been obtained, thus far, as cleavage products of nucleins, 

 and these do not always have a primary origin. In regard to the purine 

 bodies from other substances we refer the reader to their respective 

 chapters. Only the above four bodies, the real nuclein bases, will be 

 considered at this time. 



Of these four bodies xanthine and guanine form one special group 

 and hypoxanthine and adenine another. By the action of nitrous acid 

 uanine is converted into xanthine and adenine into hypoxanthine. 



C 5 H 4 N 4 O.NH + HN0 2 = C 5 H 4 K 4 O 2 + N 2 + H 2 O ; 



Guanine Xanthine 



C 5 H 4 N 4 .NH + HNO 2 + C 5 H 4 N 4 O f N 2 + H 2 O. 



Adenine Hypoxanthine 



Similar transformation, where xanthine and hypoxanthine are pro- 

 duced secondarily, may also occur in the hydrolysis of nucleic acids as 

 well as in putrefaction and by the action of special enzymes. The 

 researches of SCHITTENHELM, LEVENE, JONES, PARTRIDGE, WINTERNITZ, 

 and BURIAN 2 have shown that in various organs deamination enzymes, 

 such as guanase and adenase, occur, which convert guanine and adenine 

 into xanthine and hypoxanthine respectively, and also oxidases which 

 oxidize hypoxanthine into xanthine and this then into uric acid. This 

 formation of uric acid from the purine bases, which will be discussed in 

 detail in a following chapter (XV), is of very great interest. In this 

 connection we must also call attention to the fact, as shown by SUNDVIK, S 

 that by reduction of uric acid in alkaline solution two bodies may be 

 obtained which, although not quite identical with xanthine and hypo- 

 xanthine, are at least bodies very similar thereto. 



According to BURIAN 4 the purine bases give beautiful red products 

 with diazo-compounds as long as the imide hydrogen in the 7th position 

 (see structural formula above) is not substituted. As the nucleic acids 

 do not react with the diazo compounds, BURIAN concludes that prob- 



1 Zeitschr. f. physiol. Chem., 7. 



2 See Chapter XV (uric acid formation). 



3 Zeitschr. f. physiol. Chem., 23. 



4 Ber. d. d. chem. Gesellsch., 37 and Zeitschr. f. physiol. Chem., 42 and 51. 



