280 



PETER REICHARD 



TABLE I 

 Carbon Precursors in the Biosynthesis of Uric Acid by the Pigeon'*' '^ 



of carbon 6 of uric acid, formate almost exclusively for carbon 2 and car- 

 bon 8, and the carboxyl group of glycine for carbon 4. The incorporation 

 pattern for the two lactic acids can be explained by secondary reactions 

 such as transformation to glycine (via serine), to CO2 , and to formate 

 (via serine and glycine). The initial observation that the carboxyl group 

 of acetate is also a precursor of carbon 2 and carbon 8 has been shown to 

 be erroneous by Elwyn and Sprinson^* and by Schulman et al}^ 



The findings of Buchanan and co-workers have been confirmed and 

 extended in several different laboratories. Karlsson and Barker^" confirmed 

 the earher results with C^''02 , foi'mate-C''' and glycine-l-C*. An investi- 

 gation with glycine-2-C'^ showed that although carbon 5 of uric acid con- 

 tained 52 % of the total activity present, carbon 2, carbon 8, and to a smaller 

 extent carbon 4 of uric acid also contained C^''. These findings should be 

 compared with the results of Elwyn and Sprinson,'* who showed that ad- 

 ministration of serine-i3-C^* causes labeling of the uric acid of pigeons 

 chiefly in positions 2 and 8. According to Sakami-^ a-labeled glycine is 

 converted to a:,/3-labeled serine. The jS-carbon of serine is then transformed 

 into formate or into the same "1-C" derivative that is utihzed for the es- 

 tablishment of positions 2 and 8 in uric acid. Other amino acids which can 

 give rise to this formate derivative are L-histidine-2-C^'' ^^ and L-threo- 

 nine-2-C'^2^ The latter amino acid, however, is converted to a-labeled 

 glycine and therefore contributes most of its label to position 5 in uric 

 acid. A specific role for the whole serine molecule has been postulated by 



18 D. Elwyn and D. B. Sprinson, J. Biol. Chem. 184, 465 (1950). 



19 M. P. Schulman, J. C. Sonne, and J. M. Buchanan, /. Biol. Chem. 196, 499 (1952). 



20 J. L. Karlsson and H. A. Barker, J. Biol. Chem. 177, 597 (1949). 



21 W. Sakami, /. Biol. Chem. 176, 995 (1948). 



" D. B. Sprinson and D. Rittenberg, J. Biol. Chem. 198, 655 (1952). 



"A. 1. Krasna, P. Peyser, and D. B. Sprinson, /. Biol. Chem. 198, 421 (1952). 



