From Big Medical Encyclopedia

URIDYN — l - p - D - ribofuranozil-uracil, 2 '-dezoksiribonukleozid uracil, a natural nucleoside, one of the major metabolites participating in biosynthesis of nucleic acids and coenzymes has universal value in wildlife, is present at all animals and vegetable fabrics. Nek-ry derivatives At. and 2 '-dezoksiuridi - on, napr, f a Torah r acyl (see), are used for chemotherapy of malignant tumors thanks to effective inhibition by these compounds of enzyme thymidylate-sintetazy, a privodyashchekhma to disturbance of system of DNA repair (see. Deoxyribonucleic acid), synthesis of defective protein (see the Mutation) and, finally, to so-called bestiminovy death of a tumor cell.

Fiziol. value U. it is connected with its role of the predecessor of uridilovy nucleotides (see Uridinfosforny acids). Mono - di - and trifosfori-lirovanny derivatives At. take the important place in biosynthesis and metabolism of nucleic acids (see), in phosphoric exchange (see) and at of l ev odes of N of ohms about bm Yeon (with m).

At. the fl-N-pentatruck-nozid of heterocyclic base of a pirimidinovy kernel (see the Pirimidinovy bases) — the uracil characteristic of RNA represents (see). At. let's well dissolve in water and water solutions of ethanol, acids, alkalis; it is insoluble in the concentrated alcohol and ether. It has an appearance of colourless crystals of an acerate or prismatic form with t°li4 K.Z:» 0 KN) °.

N-glikozpdnaya communication between a D-ribose and With, - atom of heterocyclic base in a molecule U. it is very steady in neutral and alkaline environments and it is split only after long boiling in concentrated salt to - those with formation of a free D-ribose and uracil. At. possesses a maximum of absorption, characteristic of all nucleosides, at 262 pm. Identification and quantitative definition At. make hromatografichesk or spektrofotometrichesk, and also by means of the corresponding staining reactions, to-rye carry out after recovery or bromination At.

At., being a part of RNA, enters specific interactions of a complement-tsionnye with nucleosides of other polynucleotides: the rest of uracil (U) of uridine is capable to form complementary couples with nitrogen base adenine (A), a component of a nucleoside of adenosine less often with the guanine (G) which is a component of a nucleoside of guanine riboside. Couples And — Wu Yi — At are stabilized by hydrogen bindings. As a part of nucleinic to - t At. under action UF-izlu-cheniya about 5,6 dihydrouridines can be hydrogenated, and also be exposed photodimerizations that leads to serious violations of functions of polynucleotides.

As a part of nek-ry types of natural RNA meets S-glikozid-ny isomer U. — the pseudo-uridine (5-P-D-ribofuranozilura tsit) differing from At. only nature of a glycosidic linkage: in its molecule the Matchmaker of a D-ribose it is connected S-gliko-zidnoy by communication with S5-or C6-ato-mom of a pirimidinovy ring At.

Unlike At. pseudo-uridine is extremely steady in the conditions of acid hydrolysis. In a polynucleotide - ache chains it is formed as a result of intramolecular rearrangement At., carried out in the enzymatic way.

Various derivatives At. — di hydrouridines, methyluridine, tiouri-dynes, ribotimidin — are found in a number of natural RNA among so-called minor nucleosides.

In DNA of nek-ry types in trace amounts uridine is found 2 '-dezoksi ~, the carbohydrate component to-rogo is presented 2' - dezoksi - D - a ribose.

In an organism At. it can be synthesized from uracil by means of the reaction catalyzed by Uri-dinfosforilazoy enzyme. This reaction is reversible and can lead to a phosphorolysis At. At zymolysis of RNA under the influence of ribonucleases (see) and a nucleotide of az (see) also it is formed At. Catabolic transformations At. in tissues of mammals consist in splitting of a N-glycosidic linkage under the influence of specific nucleosidase, recovery of the formed uracil in its dihydroderivative, the disconnection of a heterocycle leading to formation of the l corresponding an ureide okis from and removal of ammonia and carbon dioxide; are as a result formed (3 alanines or its metilirovanny derivatives.

Receive At. zymolysis of RNA the RNA Hadean with the subsequent hydrolysis of the formed products phosphomonoesterase, and also in a synthetic way.

Bibliography: Davidson D. Biot

chemistry of nucleic acids, the lane with English, M., 1976; Organic chemistry of nucleic acids, under the editorship of N. K. Kochetkov and E. I. Budovsky, M., 1970; Sha oh

ditch and 3. And. and Bogdanov of A. A. Himiya of nucleic acids and their components, M., 1978.

P. L. Ivanov.