Nitrogenous base Nucleoside Deoxynucleoside
Chemical structure of adenine
Chemical structure of adenosine
Chemical structure of deoxyadenosine
Chemical structure of guanine
Chemical structure of guanosine
Chemical structure of deoxyguanosine
Chemical structure of thymine
Chemical structure of 5-methyluridine
Chemical structure of thymidine
Chemical structure of uracil
Chemical structure of uridine
Chemical structure of deoxyuridine
Chemical structure of cytosine
Chemical structure of cytidine
Chemical structure of deoxycytidine

Nucleosides are glycosylamines consisting of a nucleobase (often referred to as simply base) bound to a ribose or deoxyribose sugar via a beta-glycosidic linkage. Examples of nucleosides include cytidine, uridine, adenosine, guanosine, thymidine and inosine.

Biological function

Nucleosides can be phosphorylated by specific kinases in the cell on the sugar's primary alcohol group (-CH2-OH), producing nucleotides, which are the molecular building-blocks of DNA and RNA.

Nucleosides can be produced by de novo synthesis pathways, in particular in the liver, but they are more abundantly supplied via ingestion and digestion of nucleic acids in the diet, whereby nucleotidases break down nucleotides (such as the thymidine monophosphate) into nucleosides (such as thymidine) and phosphate. The nucleosides, in turn, are subsequently broken down:

  • in the lumen of the digestive system by nucleosidases into nucleobases and ribose or deoxyribose.

In addition, nucleotides can be broken down:

  • inside the cell into nitrogenous bases, and ribose-1-phosphate or deoxyribose-1-phosphate.

Use in medicine and technology

In medicine several nucleoside analogues are used as antiviral or anticancer agents. The viral polymerase incorporates these compounds with non-canonical bases. These compounds are activated in the cells by being converted into nucleotides, they are administered as nucleosides since charged nucleotides cannot easily cross cell membranes.

In molecular biology, several analogues of the sugar backbone exist. Due to the low stability of RNA, which is prone to hydrolysis, several more stable alternative nucleoside/nucleotide analogues that correctly bind to RNA are used. This is achieved by using a different backbone sugar. These analogues include LNA, morpholino, PNA.

In sequencing, dideoxynucleotides are used. These nucleotides possess the non-canon sugar dideoxyribose, which lacks 3' hydroxyl group (which accepts the phosphate) and therefore cannot bond with the next base, terminating the chain, as DNA polymerases cannot distinguish between it and a regular deoxyribonucleotide.

The structure elements of the nucleosides and the phosphate group bearing nucleotides

See also

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Look at other dictionaries:

  • nucléoside — [ nykleozid ] n. m. • 1907; de nuclé(o) et oside ♦ Biochim. Produit de décomposition partielle d un nucléide, constitué par du ribose ou du désoxyribose et une base purique ou pyrimidique. ● nucléoside nom masculin Composé formé par l union… …   Encyclopédie Universelle

  • Nucleoside — Nucléoside Les nucléosides sont des glycosylamines faites par le rattachement d une nucléobase à un cycle ribose. Dans les cellules, les nucléosides peuvent être phosphorylés par des kinases spécifiques, ce qui produit des nucléotides, les… …   Wikipédia en Français

  • nucleoside — ucleoside n. (Biochem.) A type of molecule found in all living organisms, present mostly in chemically combined form as a component of nucleic acids, and also in smaller amounts in free form, consisting of a pentose sugar bound to a purine or… …   The Collaborative International Dictionary of English

  • nucleoside — nucleoside. См. нуклеозид. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Nucleoside — Nucleoside, Verbindungen einer Purin oder Pyrimidinbase mit einer Pentose (Ribose oder Desoxyribose); Bestandteile der ⇒ Nucleotide. N. sind z.B. Adenosin, Cytidin, Uridin, Thymidin, Guanosin. Die N. sind N glykosidische Verbindungen, d.h. ein N… …   Deutsch wörterbuch der biologie

  • nucleoside — [no͞o′klē ō sīd΄, nyo͞o′klē ō sīd΄] n. [< NUCLEO + OSE2 + IDE] any of various compounds consisting of a purine or pyrimidine base linked to a carbohydrate: a major component of a nucleotide …   English World dictionary

  • Nucleoside — Die Artikel Nukleotid und Nukleoside überschneiden sich thematisch. Hilf mit, die Artikel besser voneinander abzugrenzen oder zu vereinigen. Beteilige dich dazu an der Diskussion über diese Überschneidungen. Bitte entferne diesen Baustein erst… …   Deutsch Wikipedia

  • Nucléoside —  Ne doit pas être confondu avec nucléotide. Les nucléosides sont des glycosylamines constitués d une nucléobase (ou base) liée à un ribose ou un désoxyribose via une liaison glycosidique. Parmi les nucléosides, on retrouve par exemple la… …   Wikipédia en Français

  • nucleoside — A base (purine or pyrimidine) that is covalently linked to a 5 carbon (pentose) sugar. When the sugar is ribose, the nucleoside is a ribonucleoside; when it is 2 deoxyribose, the nucleoside is a deoxyribonucleoside. See: nucleotide …   Glossary of Biotechnology

  • nucleoside — nu·cle·o·sì·de s.m. TS biochim. composto organico presente nelle nucleoproteine derivante dalla scissione di un nucleotide, formato da uno zucchero, spec. pentoso o esoso, e legato a un composto basico azotato {{line}} {{/line}} DATA: 1933. ETIMO …   Dizionario italiano

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