THE NUCLEOPROTEIDS. 293 



various phases of this conversion. We have also called attention to the 

 fact that the tissues of many organs contain ferments which are capable 

 of breaking down the nucleoproteids into their components, and finally 

 disintegrating the separate cleavage-products, such as the nucleic acids, 

 into their simpler components. The individual purine bases are changed 

 eventually by ferments into uric acid, as has been unquestionably proved 

 by the above investigators. Schittenhelm has proved that when the 

 pulp, or extract of organs, is first boiled, no uric acid can be obtained. 

 He finally succeeded in isolating the ferment producing uric acid 

 from the organs. Instead of employing organ extracts, we can now 

 utilize active ferment solutions for the experiments. The advantage of 

 this method is evident when we appreciate the fact that the pulp, or 

 extract of organs, necessarily contains varying amounts of purine bases, 

 which are practically absent from the isolated ferment or in its solutions. 

 Schittenhelm obtained xanthine on adding the ferment from beef-spleen 

 to guanine out of contact with the air, but, by conducting air through the 

 liquid, uric acid resulted. The transformation of guanine into uric acid 

 accordingly takes place with the intermediate formation of xanthine. The 

 following formulae indicate these changes: 



HN CO HN CO HN CO 



II II II 



NH 2 . C C NH > C =O C NH > CO C NH 



\ 



CH 



CH 



CO 



;_ N HN' C N HN C NH 



Guanine Xanthine Uric acid 



Guanine is converted by hydrolysis into xanthine by the loss of an NH 2 

 group. By the oxidation of xanthine, uric acid is formed. Two ferments, 

 therefore, participate in the conversion of guanine into uric acid. In the 

 same manner adenine goes over into hypoxanthine, which is then converted 

 into xanthine, and the latter into uric acid: 



N=C.NH 2 HN CO 



II II 

 HC C NH > HC C-NH > 



CH 



CH 



N C N N C N 



Adenine Hypoxanthine 



HN CO HN CO 



II II 



COC NH > CO C-NH 



\ 



CH 



\ 



/ 



HN C X HX C NH 



Xanthine Uric acid 



CO 



