Thymidine

Thymidine is a pyrimidine deoxynucleoside. It is a glycosylated pyrimidine analog and can be phosphorylated to triphosphates. Thymidine is a component of DNA and as such is important in the replication of the genome in cell division.

Structure

Thymidine is composed of a pyrimidine base, known as thymine, and a deoxyribose sugar. The thymine base is a heterocyclic aromatic compound, while the deoxyribose sugar is a pentose sugar. The two components are linked together by a β-N-glycosidic bond.

Function

Thymidine is a critical component of DNA, where it pairs with adenine via two hydrogen bonds. This pairing is crucial for the stability of the DNA double helix structure. Thymidine is also involved in the regulation of the cell cycle, as it is a necessary component for DNA synthesis during the S phase.

Synthesis

Thymidine can be synthesized in the body from deoxyuridine monophosphate (dUMP) via the action of the enzyme thymidylate synthase. This reaction also requires folate as a co-factor. Alternatively, thymidine can be salvaged from the breakdown of DNA and re-incorporated into new DNA.

Clinical significance

Thymidine analogs, such as azidothymidine (AZT), are used in the treatment of viral infections, such as HIV. These analogs act by inhibiting the reverse transcriptase enzyme, thereby preventing the replication of the viral genome.

See also

• Deoxyribose
• Pyrimidine
• Thymine
• DNA
• Cell cycle
• Thymidylate synthase
• Folate
• Azidothymidine

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