There are 4 purines and 4pyrimidines that are of concern to us.

Biosynthesis of the pyrimidine ring. Precursors of the ring and numbering of the ring atoms.

Purine and Pyrimidine Nucleotide Biosynthesis - YouTube

Evans DR and Guy HI (2004) Mammalian pyrimidine biosynthesis: fresh insights into an ancient pathway. Journal of Biological Chemistry 279: 33035–33038.

Most intracellular purine bases are salvaged and pyrimidine salvage probably occurs.

Purine Nucleotide | Nucleotides | Biosynthesis - Scribd

Hypoxanthine and xanthine are notincorporated into the nucleic acids as they are being synthesized but are importantintermediates in the synthesis and degradation of the purine nucleotides.

The detailed pathway of purine biosynthesis wasworked out primarily by Buchanan and G.

Clearly, there could not be a direct one-to-one correlation of bases to aminoacids, so the nucleotide letters must form short words or codons thatdefine specific amino acids.

The anti-codon consists of a nucleotide triplet thatis the complement of the amino acid's codon(s).

Regulation of Purine Nucleotide Biosynthesis - YouTube

Nucleotides play a variety of important roles in all cells. They are the activated precursors of DNA and RNA. ATP, an adenine nucleotide, is a universal currency of energy in biological systems. GTP is an essential carrier of chemical energy. Adenine nucleotides are components of the coenzymes NAD+, NADP+, FMN, FAD and Coenzyme A. IMP is synthesized from ribose 5-phosphate. There are 11 reactions in the formation of IMP. Nucleoside monophosphates are converted to nucleoside diphosphates by base specific monophosphate kinases. Purine nucleotide synthesis is regulated by feedback inhibitor – AMP, GMP and IMP. Recycling of purines formed by the degradation of nucleotides is possible. Pyrimidine ring is synthesized as free pyrimidine and then it is incorporated into the nucleotide. Nucleotides of a cell undergo continuous turnover. Uric acid is the breakdown product of purine nucleotide. Gout is a disease characterized by elevated levels of uric acid in body fluids. Pyrimidines on degradation give rise to carbon dioxide, ammonia, β-alanine and β-amino isobutyrate.

purine ribonucleotide biosynthetic process - Wikidata

Zhao H, French JB, Fang Y and Benkovic SJ (2013). The purinosome, a multi‐protein complex involved in the de novo biosynthesis of purines in humans. Chemical Communications 49: 4444–4452.


Salvage enzymes vary considerably in tissue distribution and specificity. Mammalian cells salvage purines primarily at the free base level through the action of two phosphoribosyltransferases: hypoxanthine guanine phosphoribosyltransferase (HGPRT), which converts hypoxanthine and guanine to inosinic acid (IMP) and GMP, respectively; and adenine phosphoribosyltransferase (APRT), which specifically converts adenine to AMP. HGPRT is the enzyme missing in cells of males suffering from Lesch-Nyhan syndrome (see Purine Ribonucleotide Metabolism). Pyrimidines, by contrast, are more likely to be salvaged at the nucleoside level. In the de novo pathway, orotic acid is converted to orotidylate by a phosphoribosyltransferase, but comparable pyrimidine salvage enzymes are of extremely limited distribution.


Eriksson S and Wang L (2008) Molecular mechanisms of mitochondrial DNA depletion diseases caused by deficiencies in enzymes in purine and pyrimidine metabolism. Nucleosides, Nucleotides & Nucleic Acids 27: 800–808.