FORMATION OF URIC ACID. 667 



At present it is considered that a direct formation of uric acid from the 

 nucleins takes place by the transformation of the purine bases of the 

 nucleins into uric acid. 



The uric acid, in so far as it is produced from nuclein bases, is in part 

 derived from the nucleins of the destroyed cells of the body and in part 

 from the nucleins or free purine bases introduced with the food. It 

 is therefore possible to admit with BURIAN and SCHUR l of a double origin 

 for the uric acid as well as the urinary purines (all purine bodies of the 

 urine, including the uric acid), namely, an endogenous and an exogenous 

 origin. BURIAN and SCHUR attempted to determine the quantity of 

 endogenous urinary purines by feeding with sufficient food, but as free 

 as possible from purine bodies, and they found that this quantity was 

 constant for every individual, while it was variable for different persons. 

 The observations of SIVEN, RocKwooD, 2 and many others have also 

 led to the same results. Other investigators have arrived at different 

 results, or they draw different deductions from their observations; still 

 this does not change the essential fact that the uric acid originating 

 from the nucleins is partly endogenous and partly exogenous, and that 

 the amount of endogenous uric acid is only very slightly dependent upon 

 the protein content of the food. 



In man and other mammalia the greatest amount if not all of the uric 

 acid originates from the nucleins or the purine bases. This formation 

 of uric acid seems to be of an enzymotic kind. After it was shown that 

 certain organs, such as the liver and spleen, had the power of converting 

 oxypurines into uric acid in the presence of oxygen (HORBACZEWSKI, 

 SPITZER and WIENER 3 ), recently SCHITTENHELM, BURIAN, JONES and 

 PARTRIDGE, 4 by more careful investigations have shown that enzymes 

 of different kinds act together. By means of the two deamidizing enzymes 

 adenase and guanase the adenine and guanine are transformed into 

 hypoxanthine and xanthine respectively, and from the latter by means 

 of an oxidizing enzyme, called xanthine oxidase by BURIAN, the uric 

 acid is formed. In the formation of uric acid from the nucleoproteins 

 we must admit of a gradual decomposition of these by the aid of different 

 enzymes, proteases, nucleases and deamidases. The deamidases seem 

 to be present in most organs, and we have numerous investigations upon 

 their distribution, especially those of JONES and SCHITTENHELM and 



1 Pfliiger's Arch., 80, 87, and 94. 



2 Siven, 1. c.; Rockwood, Amer. Journ. of Physiol., 12. 



3 See footnote 6, page 666. 



4 Schittenhelm, Zeitschr. f. physiol. Chem., 42, 43, 45, 46, 57, with Schmid, ibid., 

 50 and Zeitschr. f. exp. Path. u. Therap., 4; Burian, Zeitschr. f. physiol. Chem., 43; 

 Jones and Partridge, ibid., 43; Jones with Winternitz, ibid., 44 and 60; Jones, ibid., 

 45, with Austrian, ibid,., 48. 



