CHAPTER 25 



Biosynthesis of Nucleic Acids 



GEORGE BOS WORTH BROWN and PAUL M. ROLL 



Page 



I. Introduction 342 



1. Non-essentiality of Nucleic Acid Constituents in Mammalian Nutrition 342 

 II. The Nature of the Substances Which Can be Utilized as Polynucleotide Pre- 

 cursors 343 



1. Precursors of the Polynucleotide Purines 344 



a. Adenine and Derivatives 344 



b. Guanine and Derivatives 346 



c. Other Purines and Derivatives 347 



d. The Maintenance of the Integrity of the Purine Skeleton 348 



2. Precursors of Polynucleotide Pyrimidines 349 



a. Pyrimidines 349 



b. Pyrimidine Derivatives 350 



c. Specific Precursors of the DNA Bases 350 



3. A Summary of Compounds Used as Polynucleotide Precursors in the Rat 351 



4. Comparative Biochemistry of Purine Utilizations 353 



III. Comparative Incorporations into Various Nucleic Acid Fractions .... 356 



1. Relative Incorporations into Various Tissues 357 



a. Incorporations into DNA's of Individual Organs 357 



b. Incorporations into PNA's of Individual Organs 361 



2. Relative Incorporation into PNA and DNA of Liver 364 



a. Phosphate 364 



b. Precursors of the Carbon-Nitrogen Skeleton 365 



IV. Factors Influencing Polynucleotide Biosynthesis 375 



1. Role of Vitamins 376 



a. Folic Acid 376 



b. Vitamin Bi2 377 



c. Other Vitamins 378 



d. Other Drugs 378 



2. Role of Hormones 379 



V. Present Possibilities for Pathways of Assembly of Polynucleotides . . . 379 



1. Relation of Synthesis de novo to Incorporations of Larger Precursors . 380 



a. The Directness of the Incorporation of Exogenous Adenine .... 380 



b. Interconversions of the Purines 381 



c. Pyrimidine Derivatives 382 



2. The Alternative Metabolic Fates of Administered Compounds .... 383 

 a. Correlations with Known Mammalian Enzymes 383 



3. Polynucleotide Synthesis in L. casei 384 



4. The Synthesis of Virus Nucleic Acids 387 



341 



