RIBOSE

From Big Medical Encyclopedia

RIBOSE (C 5 H 10 O 5 ) — the monosaccharide relating to group of aldopentoses, a universal structural component of many biologically important connections, including RNA.

The river exists in the form of optically active D-and L-of forms and optically an inactive racemate — D, L-riboses. Each of these forms can form opened — aldehydic (alriboza) and cyclic — furanozny (ribofuranoza) of a form.

In the nature there is only a D-ribose, the L-ribose is received by chemical synthesis. In a free look the D-ribose in a human body and animals is not found, and only insignificant quantities it are found in urine of the person, but R. in a furanozny form is a part RNA (see), nucleosides, nucleotides, nek-ry coenzymes (see) and polysaccharides of a bacterial origin (see. Polysaccharides ). Dezoksiproizvodnoye R. — desoxyribose (see) — is a part deoxyribonucleic acid (see).

The D-ribose crystallizes in the form of colourless, strongly hydroscopic plates with t°pl 86 — 87 °, well a rastvorima in water, it is worse — in alcohol, is not ether-soluble; [a] D-— 23,7 °. The ribose has reducing power, it recovers solution of Felinga and caustic silver in alkaline condition, gives staining reactions in acid medium with aniline, barbituric and thiobarbituric to-tami, with fluoroglyutsiny, ortsiny and benzidine. During the heating in acidic environment P. forms furfural (see). The ribose can form hydrazones, osazones (see), About - and N-glycosides (see. Glycosides ). At R.'s oxidation it turns out at first monobasic ribonic to - that, and then double-base trioksiglutarovy to - that. At R.'s recovery pentatomic alcohol is formed it is beaten (ribitol, adonit), to-ry is a part of Riboflavinum and nek-ry coenzymes, in a liver it is beaten can be oxidized enzymatically in D-ribulose (see. Ribulose ).

The D-ribose is received step hydrolysis of RNA of yeast or Epi-merizatsiyey by D-pectine sugars in alkaline condition and other methods.

Qualitative test of R. is based on staining reactions, to-rye it gives in acid medium — Bial, Tauber, Benedict, Tollens's tests, etc. (see. Carbohydrates ); quantitative definition of R. in biol. liquids carry out after its allocation by methods chromatography (see) or electrophoresis (see).

The free R. which is contained in food and the majority of mammals is practically not acquired and allocated with a human body with urine that is the reason fiziol. pentosurias (see), and with a stake. In a human body and animals phosphoric ethers P., in particular ribozo-5-phosphate are metabolized, to-ry is an intermediate product of a fosfoglyukonatny (pentozo-phosphatic) way (see. Carbohydrate metabolism ). Ribozo-5-phosphate in cytoplasm of zooblasts is formed of phosphohexoses under the influence of a number of enzymes — fosfopentozo-isomerases (KF 5.3.1.6), transketo-elements (KF 2.2.1.1), transzymohexases (KF 2.2.1.2), etc., and used in synthesis of nucleotides and nek-ry coenzymes. In green plants ribozo-5-phosphate is formed at early stages photosynthesis (see). In cells of yeast and microorganisms formation of ribozo-5-phosphate to straight lines is possible phosphorylation (see) from a D-ribose and ATP under the influence of a ribokinaza (KF 2.7.1.15) «Other fosforilirovanny derivative riboses also take part in synthesis of nucleotides: ribozo-1-phosphate and 5-phosphoribosyl-1-pyrophosphate.



Bibliography: Kochetkov N. K., etc. Chemistry of carbohydrates, page 15, etc., M., 1967; Lenindzher A. Biochemistry, the lane with English, page 25, etc., M., 1976; Michel-s about n A. M of The chemistry of nucleosides and nucleotides, L. — N. Y., 1963.


V. K. Gorodetsky.

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