Purines


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Purines

 

a group of natural nitrogenous heterocyclic compounds having a purine-type molecular structure. The structure of purine is

Both in the free state and as constituents of more complex compounds, purines play a key role in the life processes of all organisms. For example, the composition of nucleic acids includes the purine compounds adenine (6-aminopurine) and guanine (2-amino-6-oxypurine) and in some cases includes smaller quantities of methylated adenines, such as 6-methylamino-purine. In ribonucleic acids (RNA), the purine compounds are combined with ribose by a glycoside bond, and in deoxyribonucleic acids (DNA), with deoxyribose by a bond to the nitrogen atom in the 9 position of purine. The content of purines in DNA is equal to that of the pyrimidine bases, while in RNA the amount of purines is usually higher than that of the pyrimi-dines. In nucleic acids, both the purine and pyrimidine compounds effect the coding of hereditary information and its replication during protein biosynthesis.

Nucleotides containing adenine play an important role in bioenergetics; adenosine triphosphate (ATP), for example, is a universal participant in the energy exchange that occurs in living cells. Guanosine triphosphate is necessary for the realization of protein biosynthesis. Cyclic adenosine 3′: 5′-mono-phosphate (cyclic AMP) is an important link in the hormonal regulation mechanism. Purine compounds are also included in the composition of many coenzymes.

Examples of purine compounds are caffeine (contained in coffee and tea), theobromine (contained in the seeds of the cacao tree), hypoxanthine, and xanthine. In higher organisms, the synthesis of purine compounds, in nucleotide form, is effected mainly in the liver; inosine monophosphate serves as a universal intermediate during the final stages of this process. The degradation of purine compounds in various groups of organisms leads to the formation of various final products, such as uric acid, allantoin, and urea.

REFERENCES

Michelson, A. M. Khimiia nukleozidov i nukleotidov. Moscow, 1966. (Translated from English.)
Davidson, J. N. Biokhimiia nukleinovykh kislot. Moscow, 1968. (Translated from English.)
Organicheskaia khimiia nukleinovykh kislot. Moscow, 1970.
Dagley, S., and D. E. Nicholson. Metabolicheskie puti. Moscow, 1973. (Translated from English.)
The Purines: Theory and Experiment. (The Jerusalem Symposia on Quantum Chemistry and Biochemistry, vol. 4.) Jerusalem, 1972.

A. S. ANTONOV

References in periodicals archive ?
Beer ingestion was most strongly correlated with hyperuricemia and gout (presumably because of the very high content of purines in beer and ale), hard liquor consumption increased serum urate and risk of gout to an intermediate degree, but moderate consumption of wine had little or no effect on either serum urate levels or the risk of gout.
A second patent application covers the use of uridine and TAU for the correction of defects in purine metabolism which produce the symptoms of autism or pervasive developmental disorder.
The nucleotides of the purines adenine and hypoxanthine yield mainly 3[prime],5[prime]-linked phosphodiester bonds (67% and 90%, respectively), while the pyrimidine nucleotides of uracil and cytosine yielded predominantly 2[prime],5[prime]-linked nucleotides (50%-75%).
* An enzyme defect that interferes with the way the body breaks down purines causes gout in a small number of people.
This meant that the number of purine units was equal to the number of pyrimidine units.
There are two ways to get purines, one is from the diet and the other is from making it in the body.
Total excretion of purine derivatives (PD) expressed in mmol/d was calculated by the sum of the excretions of allantoin and uric acid in the urine, and by the amount of allantoin excreted in the milk.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) cited, meats and other animal protein-such as eggs and fish-contain purines, which break down into uric acid in the urine.
The guidelines also advise reducing cola intake and limiting consumption of foods containing oxalate (such as beets, rhubarb, spinach, strawberries, nuts, chocolate, tea, and wheat bran) and purines (found in asparagus, bacon, beef, oysters, shellfish, and venison, among others).