The Functions of B-Vitamins in the Biosynthesis of Purines and Pyrimidines

Abstract

Publisher Summary This chapter focuses on the functions of B-vitamins in the biosynthesis of purines and pyrimidines. Since the classical discovery of uric acid as a constituent of urine, a considerable number of other purines and pyrimidines have been found to occur naturally. Of these, adenine (6-aminopurine), guanine (2-amino-6-hydroxypurine), uracil (2,4-dihydroxypyrimidine), cytosine (4-amino-2-hydroxypyrimidine), and thymine (2,4-dihydroxy-5-methylpyrimidine) are of major interest because these compounds occur as polymeric phosphorylated ribosides and desoxyribosides in the nucleic acids. Experimental studies demonstrate that the incorporation of the single carbon unit derived from formate into positions 2 and probably 8 of the purines and into the 5-methyl group of thymine involves certain B-vitamins as catalytic factors. The vitamin B 12 group and either p -aminobenzoic acid or folic acid, depending upon the organism, are involved in the utilization of the single carbon unit in a number of transformations, and this single carbon unit may be transferred from one of these products to another through these reactions. This chapter discusses B-vitamins involved in the utilization of the single carbon unit and in the oxidation of purines. This chapter analyzes the role of folic acid in the biosynthesis of purines, pyrimidines, and related factors.