Purine is a heterocyclic aromatic organic compound that consists of two rings. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines and their tautomers. They are the most widely occurring nitrogen-containing heterocycles in nature.Purines are found in high concentration in meat and meat products, especially internal organs such as liver and kidney. In general, plant-based diets are low in purines. Examples of high-purine sources include: sweetbreads, anchovies, sardines, liver, beef kidneys, brains, meat extracts (e.g., Oxo, Bovril), herring, mackerel, scallops, game meats, beer (from the yeast) and gravy. Some legumes, including lentils and black eye peas, are considered to be high purine plants. Foods and supplements containing spirulina can be exceptionally high in purines.A moderate amount of purine is also contained in red meat, beef, pork, poultry, fish and seafood, asparagus, cauliflower, spinach, mushrooms, green peas, lentils, dried peas, beans, oatmeal, wheat bran, wheat germ, and haws.Purines and pyrimidines make up the two groups of nitrogenous bases, including the two groups of nucleotide bases. The purine nucleotide bases are guanine (G) and adenine (A) which distinguish their corresponding deoxyribonucleotides (deoxyadenosine and deoxyguanosine) and ribonucleotides (adenosine, guanosine). These nucleotides are two of the building blocks of DNA and RNA respectively. The purine bases also play an essential role in many metabolic and signalling processes within the compounds guanosine monophosphate (GMP) and adenosine monophosphate (AMP).
In order perform these essential cellular processes, both purines and pyrimidines are needed by the cell, and in similar quantities. Both purine and pyrimidine are self-inhibiting and activating. When purines are formed, they inhibit the enzymes required for more purine formation. This self-inhibition occurs as they also activate the enzymes needed for pyrimidine formation. Pyrimidine simultaneously self-inhibits and activates purine in similar manner. Because of this, there is nearly an equal amount of both substances in the cell at all times.