298 PETER REICHARD 



In experiments with Lactobacillus bulgaricus 09 Wright et al.^^^ were able 

 to demonstrate that DL-ureidosuccinic acid (labeled with C^"* in the ureido 

 group) was as effective a precursor for the pyrimidines of nucleic acids as 

 was orotic acid (see below). Orotic acid is required by this bacterium as a 

 growth factor, and cannot be replaced by any pyrimidine derivative. "^''^^ 

 Weed and Wilson"^ have shown that this relationship is not limited to 

 Lactobacillus bulgaricus by the demonstration that labeled DL-ureidosuc- 

 cinic acid is incorporated into polynucleotide pyrimidines by the rat. 



Bergstrom et aZ."^ tested acetylhydantoin-N'* and carboxymethylidine- 

 hydantoin-N^^ in the rat without finding any conversion to polynucleotide 

 pyrimidines. A report by Wright et al.^^^ that 5-(carboxymethylidine)hy- 

 dantoin could replace orotic acid as a growth factor for Lactobacillus bulgari- 

 cus 09 was later withdrawn. ^^^ 



Another possible precursor for pyrimidines, aspartate-i3-C^^-7-C^^, was 

 tested in rat liver slices by Lagerkvist et al.^" The methylene carbon and, 

 to a less extensive degree, the carboxyl group were incorporated into poly- 

 nucleotide pyrimidines. Aspartate-N'^ was very poorly utihzed. It was ten- 

 tatively concluded that the carbon chain of aspartic acid w^as utilized after 

 deamination. Later experiments on the precursors of orotic acid, referred 

 to subsequently, make the interpretation of the results on the N'^ incor- 

 poration improbable. The later results indicated that rapid transamination 

 reactions together with a relatively high permeability barrier for aspartic 

 acid might explain the low incorporation of the N'* and that the whole 

 molecule is used as a precursor. It was originally pointed out that the inter- 

 pretation of the results was rather uncertain since no degradations of the 

 pyrimidines were performed. 



A complete degradation of uracil, permitting the isolation of all carbon 

 atoms, was devised by Lagerkvist^"^ (Fig. 9). After reduction to hydrouracil, 

 the ring was split by acid hydrolysis, and propionic acid was obtained from 

 the resulting /3-alanine via hydracrylic and acrylic acids. The carboxyl 

 carbon of the propionic acid corresponded to position 6 of uracil, the a- 

 carbon to position 5, and the /3-carbon to position 4. The propionic acid 



1" L. D. Wright, C. S. Miller, H. R. Skeggs, J. W. Huff, L. L. Weed, and D. W. Wil- 

 son, /. A}7i. Chem. Soc. 73, 1898 (1951). 



"2 L. D. Wright, J. W. Huff, H. R. Skeggs, K. A. Valentik, and D. K. Bosshardt, 

 /. Am. Chem. Soc. 72, 2312 (1950). 



"^ O. P. Wieland, J. Avener, E. M. Boggiano, N. Bohonos, B. L. Hutchings, and J. 

 H. Williams, J. Biol. Chem. 186, 737 (1950). 



'" L. L. Weed and D. W. Wilson, /. Biol. Chem. 207, 439 (1954). 



"^ S. Bergstrom, E. Hammarsten, and P. Reichard, Acta Chem. Scand. 4, 1497 (1950). 



'!« L. D. Wright, K. A. Valentik, D. S. Spicer, J. W. Huff, and H. R. Skeggs, Proc. 

 Soc. Exptl. Biol. Med. 75, 293 (1950). 



1'^ U. Lagerkvist, P. Reichard, and G. Ehrensvard, Acta Chem. Scand. 5, 1212 (1951). 



