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A purine is a bicyclic organic compound, consisting of a fused pyrimidine/ imidazole ring. Two of the bases in nucleic acids, adenine and guanine, are purines. In DNA, these bases form hydrogen bonds with their complementary pyrimidines thymine and cytosine. purine pyrimidine
A T
G C
In RNA, the complement of A is uracil instead of thymine:
purine pyrimidine
A U
G C
These hydrogen bonding modes are for classical Watson-Crick base pairing. Other hydrogen bonding modes are seen in both DNA and RNA, although the additional 2'-hydroxyl group of RNA expands the configurations through which RNA can form hydrogen bonds.
Some other purines are xanthine, hypoxanthineHypoxanthine is a naturally occurring purine derivative, and one of the products of the action of xanthine oxidase on xanthine, though more normally in purine degradation, hypoxanthine is oxidized by xanthine oxidase to form xanthine. It is very occasiona, and caffeineCaffeine is an alkaloid found naturally in such foods as coffee beans, tea, kola nuts, Yerba mate, guarana, and (in small amounts) cacao beans. It is added to some soft drinks such as colas and Mountain Dew. Caffeine has a characteristic intensely bitter.
Purines from food (or from tissue turnover) are metabolized by several enzymeAn enzyme is a protein, or protein complex, that catalyzes a chemical reaction. Like any catalyst, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to proceed to its steady state or completion much faster than it ots, including xanthine oxidaseThe enzyme xanthine oxidase or XO (bovine milk enzyme is PDB , E. 22) catalyzes the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthine to uric acid: hypoxanthine + O xanthine + HO xanthine + O + 2HO uric acid + 2HO Th, into uric acidUric acid is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula C H N O It is a minor end-product of nitrogen metabolism in the human body (the main product being urea), and is found in small amounts in urine. In some other ani. High levels of uric acid can predispose to gout when the acid crystalizes in joints; this phenomenon only happens in humans and some animal species (e.g. dogs) that lack an intrinsic urease enzyme that can further degrade uric acid.
History
Purine was named by the german chemist Emil Fisher in 1884. He synthesized it in 1898. Fisher showed that the Purines were part of a single chemical family.
Biochemicals Purines
