Purine Biosynthesis Metabolism

2. Introduction
• Purines are one of the important components of nucleotides. Purine is a heterocyclic
aromatic organic compound that consists of a pyrimidine ring fused to an imidazole ring.
• Purines are found in high concentration in meat and meat products, especially internal
organs such as liver and kidney.
• Plant-based diets are low in purines.
• Examples of high-purine sources include: Sweetbreads, anchovies, sardines, liver, beef
kidneys, brains, meat extracts etc.

3. Structure of purines
• The purine skeleton is a 6-membered pyrimidine ring fused to a 5-membered imidazole
ring.
• Each ring contains two nitrogen (N) atoms, with the remaining 5 positions in each ring
occupied by carbon (C), which is attached to a Hydrogen (H).
• Hydrogen can be replaced by different atoms or groups to form distinct purines.
• The 4 Ns originate from different amino acids and the remaining 5 Cs derive from one-
carbon containing groups

4. Figure : Structure of Purine

5. Biosynthesis

7. Succinate

8. Biosynthesis Regulation
• The pathways synthesizing IMP, ATP, and GTP are individually regulated. This is
crucial to prevent the waste of
– Energy and nitrogen,
– To control the total amounts of purine nucleotides available for nucleic acid
synthesis and
– The purine waste product, uric acid, is are harmful to cells.
• IMP synthesis is controlled by the levels of adenine and guanine nucleotides
• The second level of regulation occurs at the branch point below IMP, leading to
either AMP or GMP.

9. Conclusion
Purine synthesis and metabolism play major roles in controlling embryonic and fetal
development and organogenesis. Dynamic and time-dependent changes in the
expression of purine metabolizing enzymes (such as ectonucleotidases and adenosine
deaminase) represent a key checkpoint for the correct sequential generation of the
different signaling molecules that in turn activate their specific membrane receptors.