A role of aspartic acid in purine biosynthesis.

The incorporation of isotopic nitrogen from N15-aspartic acid, N15-glutamic acid, or N15(amide nitrogen)-glutamine into the nitrogens of the pyrimidine ring of hypoxanthine synthesized from glycine-l-Cl4 in pigeon liver extracts has been reported to be approximately equivalent to the incorporation of Cl4 from labeled glycine (1). It was proposed that biological similarity of the transaminating dicarboxylic acids favors the probability that these amino acids supplied the same nitrogen atom while the amide group of glutamine donated the other nitrogen atom of the pyrimidine ring of hypoxanthine (1). In the present investigation, aspartic acid or a biochemically related 4-carbon compound has been found to be essential for purine biosynthesis in Lactobacillus arabinosus 17-5. The interrelationship is based upon the effect of purines on the aspartic acid requirement for growth and on cysteic acid inhibition of growth.