Everything about Purine totally explained
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Purine (
1) is a
heterocyclic aromatic organic compound, consisting of a
pyrimidine ring fused to an
imidazole ring. Purines and pyrimidines make up the two groups of
nitrogenous bases. These bases make up a crucial part of both deoxyribonucleotides and ribonucleotides, and the basis for the universal genetic code.
The general term
purines also refers to substituted purines and their
tautomers.
The purine is the most widely distributed nitrogen-containing
heterocycle in nature.
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. This is called enzymes 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).
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, hasn't 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. The starting material for the reaction sequence was uric acid (
8), which had been isolated from kidney stones by Scheele in 1776. Uric acid (8) was reacted with PCl
5 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.
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
(External Link
).
Examples of high purine sources include: sweetbreads, anchovies, sardines, liver, beef, kidneys, brains,
meat extracts, 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 and wheat germ.
Moderate intake of purine-containing food isn't associated with an increased risk of
gout.
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.
Procedure:
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.
The
Traube purine synthesis (1900) is a classic reaction (named after
Wilhelm Traube) between an
amine substutited
pyrimidine and
formic acid
Further Information
Get more info on 'Purine'.
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