294 PETER REICHARD 



By the use of guanine-C'*' instead of the labeled-N^* compound, it could be demon- 

 strated by Balis et al.^" and by Abrams^' that the C^^-labeled compound was also used 

 by the rat for the synthesis of nucleic acid guanine and adenine, although to a much 

 smaller extent than was adenine. This followed the demonstration that the C 57 black 

 mouse could utilize guanine-N'^ for synthesis of nucleic acid guanine*^ and that 

 adenine-C'^ and guanine-C^^ served equally well as precursors for polj-nucleotide 

 purines in rabbit bone marrow slices.*^ 



Getler et al.^* demonstrated that neither hj^poxanthine nor xanthine were pre- 

 cursors of nucleic acid purines in the rat. These compounds had been thought to be 

 hypothetical intermediates in the transformation of adenine to guanine. The results 

 of Abrams and Goldinger,*^ which demonstrate the incorporation of hypoxanthine- 

 8-C^^ into nucleic acid purines from rabbit bone marrow slices, stress the importance 

 of keeping in mind species differences. 



Another possible intermediate, 2,6-diaminopurine, was shown by Bendich et al.^^ 

 to be exclusively incorporated into nucleic acid guanine when labeled with either N'* 

 or C" and was considered as an intermediate in the transformation of adenine to 

 guanine by the rat. 



A wealth of information on different purine utilization patterns can be obtained 

 from microbiological data. For example, many organisms can utilize both guanine 

 and adenine for growth (e.g., j-east," Lactobacillus casei,^^ and E. coW^), others have 

 more specific requirements for adenine'" which in many cases can be replaced by 

 hypoxanthine,'^ and others specifically require guanine or diaminopurine.'^'^' 



The incorporation of free adenine and diaminopurine may not proceed via the 

 corresponding nucleotides, as demonstrated by the results of Roll et al.^* and Kerr 

 et al.,^'' who found that the incorporation of the labeled mononucleotides into poly- 

 nucleotides of the rat and of yeast, respectively, was considerably lower than 

 the utilization of the corresponding free purines. The mononucleotides used in these 

 experiments were not the 5'-nucleotides, however. 



The general impression obtained from all the precursor experiments with pre- 

 formed purines is that a great diversity of biosynthetic patterns may exist. The 

 problem is complicated by the biological heterogeneity of the nucleic acids studied. 



8° M. E. Balis, D. H. Marrian, and G. B. Brown, J. Am. Chem. Soc. 73, 3319 (1951). 

 *i R. Abrams, Arch. Biochem. and Biophys. 33, 436 (1951). 



82 G. B. Brown, A. Bendich, P. M. Roll, and K. Sugiura, Proc. Soc. Exptl. Biol. 

 Med. 72, 501 (1949). 



83 R. Abrams and J. M. Goldinger, Arch. Biochem. 30, 261 (1951). 



8^ H. Getler, P. M. Roll, J. F. Tinker, and G. B. Brown, J. Biol. Chem. 178, 259 (1949) . 



85 R. Abrams and J. M. Goldinger, Arch. Biochem. and Biophys. 35, 243 (1952). 



86 A. Bendich, S. S. Furst and G. B. Brown, J. Biol. Chem. 185, 423 (1950). 

 8'S. E. Kerr, K. Seraidarian, and G. B. Brown, J. Biol. Chem. 188, 207 (1951), 



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



Hitchings, J. Biol. Chem. 196, 729 (1952). 

 8s A. L. Koch, F. W. Putnam, and E. A. Evans, Jr., J. Biol. Chem. 197, 105 (1952). 

 ^° H. K. Mitchell and M. B. Houlahan, Federation Proc. 5, 370 (1946). 

 31 J. G. Pierce and H. S. Loring, J. Biol. Chem. 160, 409 (1945). 

 s2 G. W. Kidder and V. C. Dewey, Proc. Natl. Acad. Sci. U.S. 34, 566 (1948). 

 " N. Fries, J. Biol. Chem. 200, 325 (1953). 

 '^ P. M. Roll, G. B. Brown, F. J. Di Carlo, and A. S. Schultz, J. Biol. Chem. 180, 



333 (1949). 



