346 GEORGE BOSWORTH BROWN AND PAUL M. ROLL 



was utilized to the same extent. However, adenosine-5'-phosphate-8-C^* ^^ 

 was incorporated to an appreciably smaller extent than were those three 

 compounds.^^ In all of the experiments involving adenosine and adenylic 

 acid, it was found that there was a conversion of the adenine moiety into 

 PNA guanine but that the guanine was always labeled to less than one-half 

 the extent of PNA adenine. There was at best only a small incorporation 

 of these compounds into DNA. On the basis of these results alone, the pos- 

 sibility of the incorporation of adenosine and adenylic acids into the nucleic 

 acids of the rat via a prior degradation to adenine cannot be excluded. 



The only other organisms in which the incorporation of adenosine and 

 adenylic acids have been studied are yeast and Lactobacillus casei. In yeast, 

 only a very small incorporation of any of the nucleosides or nucleotides 

 was observed.^^ On the other hand, in L. casei there was a considerable 

 utilization of these derivatives, and results with adenosine'^ parallel those 

 obtained with the rat in that the nucleoside is not utilized as well as is the 

 free base. However in L. casei adenosine-2'-phosphate is utilized scarcely 

 at all while adenosine-3'-phosphate is incorporated as well as is adenine.^' 



h. Guanine and Derivatives 



In 1944, Plentl and Schoenheimer^'' reported that dietary guanine was 

 not utilized by the rat for nucleic acid synthesis, and this result was con- 

 firmed'^'" in parallel with the experiments which revealed the incorporation 

 of adenine-1 ,3-N2'^. However, in both experiments guanine-2-ammo-l ,3- 

 Na'^ was administered so that, during the catabolism of the purine to allan- 

 toin (a process which was known to occur from the presence of highly labeled 

 allantoin in the urine), the 2-amino group contributed N'^Hs to the body 

 pool ammonia. This resulted in a small generalized labeling of all purines 

 and pyrimidines, and consequently a trace incorporation of guanine was 

 undetectable in the experiments. Subsequently, by the use of the more 

 sensitive tracer carbon-14, Balis et al}^ were able to show that guanine-8-C'* 

 was incorporated to about the extent of 0.1 % in the nucleic acid guanine 

 of the rat. Abrams'^ found that guanine-2-C'^ was incorporated to a some- 

 what greater extent into the guanine of the PNA of rat intestine, and was 



2^ Prepared by phosphorylation of synthetic adenosine-8-C''' by the use of adenosine 



phosphokinase.'" 

 3» A. Romberg and W. E. Pricer, Jr., J. Biol. Chem. 193, 481 (1951). 

 3' H. Weinfeld and P. M. Roll, Federation Proc. 12, 287 (1953). 



32 M. E. Balis, D. H. Levin, G. B. Brown, G. B. Elion, H. VanderWerff, and G. H. 

 Hitchings, J. Biol. Chem. 199, 227 (1952). 



33 M. E. Balis, D. H. Levin, G. B. Brown, G. B. Elion, H. VanderWerff, and G. H. 

 Hitchings, J. Biol. Chem. 200, 1 (1953). 



34 A. A. Plentl and R. Schoenheimer, J. Biol. Chem. 153, 203 (1944) 



35 M. E. Balis, D. H. Marrian, and G. B. Brown, /. Am. Chem. Sac. 73, 3319 (1951). 



I 



