Purine
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| Purine | |
|---|---|
| Chemical name | Purine |
| Chemical formula | C5H4N4 |
| Molecular mass | 120.11206 g/mol |
| Melting point | 214 °C |
| CAS number | 120-73-0 |
| SMILES | C1(NC=N2)=C2C=NC=N1 |
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Purine (1) is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring.
The general term purines also refers to substituted purines and their tautomers.
The purine is the most widely distributed nitrogen containing heterocycle in nature.1 The quantity of naturally occurring purines produced on earth is enormous, as 50 % of the bases in nucleic acids, adenine (2) and guanine (3), are purines. In DNA, these bases form hydrogen bonds with their complementary pyrimidines thymine and cytosine. In RNA, the complement of adenine is uracil (U) instead of thymine.
Other notable purines are hypoxanthine (4), xanthine (5), theobromine (6), caffeine (7), uric acid (8) and isoguanine (9).
Aside from DNA and RNA, purines are biochemically significant components in a number of other important biomolecules, such as ATP, GTP, cyclic AMP, NADH, and coenzyme A. Purine (1) itself, has not been found in nature, but it can be produced by organic synthesis.
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[edit] History
The name 'Purine' (purum uricum) was coined by the German chemist Emil Fischer in 1884. He synthesized it for the first time in 1899.2 The starting material for the reaction sequence was uric acid (8), which had been isolated by gallstones by Scheele in 1776.3 Uric acid (8) was reacted with PCl5 to give 2,6,8-trichloropurine (10), which was converted with HI and PH4I to give 2,6-diiodopurine (11). This latter product was reduced to purine (1) using zinc-dust.
[edit] Metabolism
Many organisms have metabolic pathways to synthesise and break down purines.
Purines are biologically synthesized as nucleosides (bases attached to ribose). Both adenine and guanine are derived from the nucleoside inosine monophosphate, which is synthesised on a pre-existing ribose through a complex pathway using atoms from the amino acids glycine, glutamine, and aspartic acid, as well as formate ions transferred from the coenzyme tetrahydrofolate.
Purines from food (or from tissue turnover) are metabolised by several enzymes, including xanthine oxidase, into uric acid. High levels of uric acid can predispose to gout when the acid crystalises in joints; this phenomenon only happens in humans and some animal species (e.g. dogs) that lack an intrinsic uricase enzyme that can further degrade uric acid. The deficiency of another enzyme, adenosine deaminase, needed to break down adenine, is a cause of severe combined immunodeficiency.
Purines from turnover of nucleic acids (or from food) can also be salvaged and reused in new nucleotides. The enzyme adenine phosphoribosyltransferase salvages adenine, while hypoxanthine-guanine phosphoribosyltransferase kiran (HPRT) salvages guanine and hypoxanthine. Genetic deficiency of HPRT causes Lesch-Nyhan syndrome.
[edit] Food Sources
Purines are found in high concentration in meat and meat products, especially internal organs such as liver and kidney. Plant based diet is generally low in purines [1].
[edit] Synthesis
Purine (1) is obtained in good yield when formamide is heated in an open vessel at 170 oC for 28 hours.4
Procedure:4 Formamide (45 gram) was heated in an open vessel with a condenser for 28 hours in an oil bath at 170-190 oC. After removing excess formamide (32.1 gram) by vacuum distillation, the residue was refluxed with methanol. The methanol solvent was filtered, the solvent removed from the filtrate by vacuum distillation, and almost pure purine obtained; yield 4.93 gram (71 % yield from formamide consumed). Crystallization from acetone afforded purine as colorless crystals; melting point 218 oC.
Oro, Orgel and co-workers have shown that four molecules of HCN tetramerize to form diaminomaleodinitrile (12), which can be converted into almost all important natural occurring purines.5-9
[edit] References
1) Rosemeyer, H. Chemistry & Biodiversity 2004, 1, 361.
2) Fischer, E. Berichte der Deutschen Chemischen Gesellschaft 1899, 32, 2550.
3) Scheele, V. Q. Examen Chemicum Calculi Urinari, Opuscula, 1776, 2, 73.
4) Yamada, H.; Okamoto, T. Chemical & Pharmaceutical Bulletin, 1972, 20, 623.
5) Sanchez, R. A.; Ferris, J. P.; Orgel, L. E. Journal of Molecular Biology, 1967, 30, 223.
6) Ferris, J. P.; Orgel, L. E. Journal of the American Chemical Society, 1966, 88, 1074.
7) Ferris, J. P.; Kuder, J. E.; Catalano, O. W. Science, 1969, 166, 765.
8) Oro, J.; Kamat, J. S. Nature, 1961, 190, 442.
9) Houben-Weyl, Vol . E5, p. 1547
[edit] See also
[edit] External links
| Major Families of Biochemicals | ||
| Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides | ||
| Analogues of nucleic acids: | Types of Nucleic Acids | Analogues of nucleic acids: |
| Nucleobases: | Adenine | Thymine | Uracil | Guanine | Cytosine | Purine | Pyrimidine | |
|---|---|---|
| Nucleosides: | Adenosine | Uridine | Guanosine | Cytidine | Deoxyadenosine | Thymidine | Deoxyguanosine | Deoxycytidine | |
| Nucleotides: | AMP | UMP | GMP | CMP | ADP | UDP | GDP | CDP | ATP | UTP | GTP | CTP | cAMP | cADPR | cGMP | |
| Deoxynucleotides: | dAMP | TMP | dGMP | dCMP | dADP | TDP | dGDP | dCDP | dATP | TTP | dGTP | dCTP | |
| Ribonucleic acids: | RNA | mRNA | piRNA | tRNA | rRNA | ncRNA | sgRNA | shRNA | siRNA | snRNA | miRNA | snoRNA | LNA | |
| Deoxyribonucleic acids: | DNA | mtDNA | cDNA | plasmid | Cosmid | BAC | YAC | HAC | |
| Analogues of nucleic acids: | GNA | PNA | TNA| LNA | morpholino | |
