THE METABOLISM OF THE PURIN BODIES :-',97 



the other hand, no xanthin and hypoxanthin or only a trace 

 could be prepared from a fresh extract of spleen. If the 

 incubated, slightly putrid mixture were supplied with oxygen 

 as by shaking it with air, or adding H 2 2 or blood to it, he 

 obtained uric acid instead of hypoxanthin and xanthin. 



That these purin bodies were actually derived from the 

 nuclein of the spleen was demonstrated by the fact that nuclein, 

 prepared from any organ or tissue by the usual methods, gave 

 similar results when treated in the same way as described above 

 for the spleen. Horbaczewski concluded from these experiments 

 that nuclein must contain some precursor from which, on its decom- 

 position, either xanthin and hypoxanthin or uric acid was produced ; 

 the former bodies when no oxygen was present in the mixture, the 

 uric acid in the presence of oxygen. He further stated that it was 

 impossible to convert xanthin bases directly into uric acid. 



Spitzer ( G ) repeated Horbaczewski' s experiments and found 

 that uric acid could be produced by merely bubbling air through 

 a watery extract of spleen pulp, in which putrefaction was pre- 

 vented by adding chloroform or thymol. Putrefaction is, 

 therefore, not necessary for the process. This worker further 

 found that xanthin and hypoxanthin could be directly converted 

 into uric acid by adding these bodies to an extract of spleen 

 or liver and bubbling air through the mixture at a temperature 

 of 50 C. Extracts of other organs, such as kidneys, thymus, and 

 pancreas could not affect this oxidation to anything like the 

 same extent as could those of the liver and spleen. 



Burian ( 35 ) has recently continued Spitzer's work on the con- 

 version of xanthin and hypoxanthin into uric acid by the liver. 

 By macerating the minced liver of the ox with ice-cold chloroform 

 water this worker has been able to prepare an extract, containing 

 only traces of nucleo-proteids and purin bodies, but possessing 

 quite a marked power of oxidising xanthin and hypoxanthin 

 into uric acid when these bodies are added to the extract, and 

 the whole incubated at body temperature in the presence of an 

 excess of oxygen. He has been able to show that this action 

 is due to an oxidising ferment xanthin-oxydase which itself does 

 not become used up during its action, and which does not show 

 any reversible action (i.e. cannot reduce uric acid to xanthin 

 bases). 



Xanthin-oxydase cannot, however, convert guanin and adenin 



