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purine

 
Dictionary: pu·rine   (pyʊr'ēn') pronunciation
n.
  1. A double-ringed, crystalline organic base, C5H4N4, not known to occur naturally, from which is derived the nitrogen bases adenine and guanine, as well as uric acid as a metabolic end product.
  2. Any of a group of organic compounds structurally related to purine, particularly adenine and guanine, and also caffeine, uric acid, theobromine, and theophylline.

[German Purin : blend of Latin pūrus, clean; see pure, and New Latin ūricus, uric (from Greek ouron, urine) + -in, -in, -ine.]


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A heterocyclic organic compound (1) 1

containing fused pyrimidine and imidazole rings. A number of substituted purine derivatives occur in nature; some, as components of nucleic acids and coenzymes, play vital roles in the genetic and metabolic processes of all living organisms. See also Coenzyme; Nucleic acid.

Purines are generally white solids of amphoteric character. They can form salts with both acids and bases. Conjugated double bonds in purines results in aromatic chemical properties, that confers considerable stability, and accounts for their strong ultraviolet absorption spectra. With the exception of the parent compound, most substituted purines have low solubilities in water and organic solvents.

The purine bases, adenine (2) and guanine (3), 2

3
together with pyrimidines, are fundamental components of all nucleic acids. Certain methylated derivatives of adenine and guanine are also present in some nucleic acids in low amounts. In biological systems, hypoxanthine (4), 4
adenine, and guanine occur mainly as their 9-glycosides, the sugar being either ribose or 2-deoxyribose. Such compounds are termed nucleosides generically, and inosine (hypoxanthine nucleoside), adenosine, or guanosine specifically. The principal nucleotides contain 5′-phosphate groups, as in guanosine 5′-phosphate (GTP) and adenosine 5′-triphosphate (ATP). See also Adenosine triphosphate (ATP).

Most living organisms are capable of synthesizing purine compounds. The sequence of enzymatic reactions by which the initial purine product, inosine 5′-phosphate, is formed utilizes glycine, carbon dioxide, formic acid, and amino groups derived from glutamine and aspartic acid. Adenosine 5′-phosphate and guanosine 5′-phosphate are formed from inosine 5′-phosphate.

Metabolic degradation of purine derivatives may also occur by hydrolysis of nucleotides and nucleosides to the related free bases. Deamination of adenine and guanine produces hypoxanthine and xanthine (5), both of which may be oxidized to uric acid (6). 5

6

Purine-related compounds have been investigated as potential chemotherapeutic agents. In particular, 6-mercaptopurine, in the form of its nucleoside phosphate, inhibits several enzymes required for synthesis of adenosine and guanosine nucleotides, and thus proves useful in selectively arresting the growth of tumors. The pyrazolopyrimidine has been used in gout therapy. As a purine analog, this agent serves to block the biosynthesis of inosine phosphate, as well as the oxidation of hypoxanthine and xanthine to uric acid. As a result of its use, overproduction of uric acid is prevented and the primary cause of gout is removed. See also Pyrimidine.


Food and Nutrition: purines
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Nitrogenous compounds (bases) that occur in nucleic acids (adenine and guanine) and their precursors and metabolites; inosine, caffeine, and theobromine are also purines. They are not dietary essentials; both dietary and endogenously formed purines are excreted as uric acid. See also gout.

Sweetbread (pancreas) is rich in purines, as is fish roe; there are moderate amounts in sardines and anchovies, lesser amounts in other fish and meat; little in vegetables, fruits, and cereals.


Any of a class of heterocyclic compounds with a two-ring structure composed of carbon and nitrogen atoms. The simplest member, purine itself (C5H4N4), is not common, but its derivatives with the structure are. Examples are uric acid, caffeine, and two of the nucleotides in nucleic acids, guanine and adenine.

For more information on purine, visit Britannica.com.

 
purine, type of organic base found in the nucleotides and nucleic acids of plant and animal tissue. The German chemist Emil Fischer did much of the basic work on purines and introduced the term into the chemical literature in the early 20th cent. The two major purines of almost universal distribution in living systems are adenine and guanine.


A heterocyclic compound that is the nucleus of the purine bases (or purines) such as adenine and guanine, which occur in DNA and RNA, and xanthine and hypoxanthine. All living cells contain purines as purine nucleotides. They can be synthesized using amino acids, or by salvage of dietary or endogenous nucleotides derived from cell wastage.

  • A p. — adenine.
  • low p. diet — one with a low content of organ meats, seafood, beans, lentils, peas and spinach; used in the dietary management of xanthine or urate uroliths in dogs.
  • p. nucleoside phosphorylase — a transferase enzyme that acts in the degradation of nucelotides and nucleic acids.
Wikipedia: Purine
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Purine
Purine chemical structure.png
IUPAC name
Identifiers
CAS number 120-73-0 Yes check.svgY
PubChem 1044
MeSH Purine
SMILES
ChemSpider ID 1015
Properties
Molecular formula C5H4N4
Molar mass 120.112
Melting point

214 °C

 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature.[1]

Purines and pyrimidines make up the two groups of nitrogenous bases, including the two groups of nucleotide bases. Two of the four deoxyribonucleotides and two of the four ribonucleotides, the respective building blocks of DNA and RNA, are purines.

Contents

Notable purines

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 respectively. This is called complementary base pairing. 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).

Purines.gif

Functions

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.

They may also function directly as neurotransmitters, acting upon purinergic receptors. Adenosine activates adenosine receptors.

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 from kidney stones 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.

FischerPurineSynthesis.gif

Metabolism

Many organisms have metabolic pathways to synthesize and break down purines.

Purines are biologically synthesized as nucleosides (bases attached to ribose).

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].

Examples of high purine sources include: sweetbreads, anchovies, sardines, liver, beef kidneys, brains, meat extracts (e.g Oxo, Bovril), herring, mackerel, scallops, game meats, and gravy.

A moderate amount of purine is also contained in beef, pork, poultry, fish and seafood, asparagus, cauliflower, spinach, mushrooms, green peas, lentils, dried peas, beans, oatmeal, wheat bran, wheat germ, and hawthorn.[4]

Higher levels of meat and seafood consumption are associated with an increased risk of gout, whereas a higher level of consumption of dairy products is associated with a decreased risk. Moderate intake of purine-rich vegetables or protein is not associated with an increased risk of gout.[5]

Laboratory synthesis

In addition to in vivo synthesis of purines in purine metabolism, purine can also be created artificially.

Purine (1) is obtained in good yield when formamide is heated in an open vessel at 170 oC for 28 hours.[6]

Purinesynthesis.gif

Procedure:[6] 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.[7][8][9][10][11]

Basicpurines.gif

The Traube purine synthesis (1900) is a classic reaction (named after Wilhelm Traube) between an amine substutited pyrimidine and formic acid [12]

Traube purine synthesis

See also

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. ^ Gout Diet: Limit High Purine Foods
  5. ^ NEJM - Purine-Rich Foods, Dairy and Protein Intake, and the Risk of Gout in Men
  6. ^ a b Yamada, H.; Okamoto, T. Chemical & Pharmaceutical Bulletin, 1972, 20, 623.
  7. ^ Sanchez, R. A.; Ferris, J. P.; Orgel, L. E. Journal of Molecular Biology, 1967, 30, 223.
  8. ^ Ferris, J. P.; Orgel, L. E. Journal of the American Chemical Society, 1966, 88, 1074.
  9. ^ Ferris, J. P.; Kuder, J. E.; Catalano, O. W. Science, 1969, 166, 765.
  10. ^ Oro, J.; Kamat, J. S. Nature, 1961, 190, 442.
  11. ^ Houben-Weyl, Vol . E5, p. 1547
  12. ^ Organic Syntheses Based on Name Reactions, Alfred Hassner, C. Stumer ISBN 008043259X 2002

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