From Big Medical Encyclopedia

PURINE BASES — derivatives of heterocyclic compound of purine, a molecule to-rogo consists of condensed nuclears of a pyrimidine and an imidazole. Genetically caused disturbance of purine exchange (see) and activities of its separate enzymes is the reason of a number of a serious hereditary illness: Lesh's syndrome — Naykhana (see. Gout ), an idiopathic family hyperuricemia (see. Lithemia ), etc. Some purine bases use in medicine as pharmaceuticals, napr, metilirovanny derivatives of purine — caffeine (see) and theobromine (see).

Purines adenine (6 aminopurine) and a guanine (2-amino-6-hypoxanthine), so-called aminopurines, are a part of nucleic acids (see), coenzymes (see) and free nucleotides.

From some nucleinic to - t were allocated the so-called minor purines different from adenine or guanine with existence alkyl (is more often than methyl), acyl and other groups.

In live organisms also P. of lakes which are not found in nucleinic to-takh meet, and are products of a catabolism of purines. These are, first of all, hypoxanthines — uric acid (see), xanthine (see) and hypoxanthine (see).

In total P. of the lake quite badly rastvorima in water. During the heating adenine and guanine do not melt, and decay at temperatures over 360 °. Water solution of adenine has alkalescent properties, and presence of OH-and NH2-group at a molecule of guanine does it by amphoteric connection owing to what it interacts with to-tami, alkalis and metals. As well as the pirimidinovy bases (see), purine bases are capable to tautomeric reorganizations: hypoxanthines — to a lactam — laktimny, and aminopurines — to amine — nominal. This property of purines plays an important role in a mutagenesis (see). Purine bases absorb light in the UF-part of a range. The maximum of absorption for adenine at pH 7,0 is at 260 nanometers, for guanine — at 276 nanometers.

Almost all living beings are capable to synthesize rings of a pyrimidine and an imidazole (see) and only some use for biosynthesis of nucleic acids only those P. of lakes which they receive with food. Rate of decay of ring system P. of the lake in the course of a metabolism varies at different types. At the person and other primacies an end product of purine exchange is uric to - that, the quantity a cut in urine normal makes 0,4 — 1 g a day. Adenine under the influence of an adeninedeaminase (KF can be hydrolytic dezaminirovan and guanine under the influence of a guanindezaminaza (KF — in xanthine is turned into hypoxanthine, and. This process can happen at the level of nucleotides and nucleosides. Further under the influence of a xanthineoxidase (KF hypoxanthine and xanthine turn in uric to - that.

The most widespread method of definition of P. of the lake is based on their ability to absorb light with certain lengths of waves UF-parts of a range. Mix P. of the lake is usually divided by means of a chromatography (see) and define spektrofotometrichesk (see. Spektrofotometriya ).

Bibliography: See bibliogr, to St. Purine exchange .

O. D. Lopina.