BIOSYNTHESIS OF PURINES AND PYRIMIDINES 



301 



TABLE IX 



Incorporation of N'^-Labeled Orotic Acid into PNA and DNA from Different 



Organs of the Rat'^-^^z 



" The purines from the DNA of liver were contaminated with other nitrogen-containing material as 

 judged by light absorption criteria. 



from animal and human tumors/" from yeast,^' and from Lactobacillus 

 bularicus 09^^^ has now been proved. In vitro incorporation of orotic acid 

 in hver slices has been demonstrated by Weed and Wilson^^' and by Reich- 

 ard and Bergstrom.^-^ 



Michelson et al.™ have isolated a nucleoside of orotic acid from the my- 

 ceha of Neurospora. The point of attachment of ribose on orotic acid was 

 not reported. In contrast to the pyrimidine nucleosides obtained from 

 polynucleotides, this riboside was acid-labile, which might well be explained 

 by the presence of the carboxyl group in position 4. On the other hand, a 

 glycosidic linkage not involving nitrogen 3 of orotic acid might be con- 

 sidered.^-* 



'" L. L. Weed, Cancer Research 11, 470 (1951). 



>26 p. Reichard and S. Bergstrom, Acta Chem. Scand. 5, 190 (1951). 



'" A. M. Michelson, W. Drell, and H. K. Mitchell, Proc. Natl. Acad. Sci. U.S. 37, 



396 (1951). 

 '^* L. D. Wright (personal communication) has found that orotidine cannot replace 



orotic acid as a growth factor for Lactobacillus bulgaricus 09. 



