Thymidine

Chemical structure of thymidine

Thymidine is a nucleoside composed of the pyrimidine base thymine attached to a deoxyribose sugar. It is one of the four nucleosides in DNA, the others being adenosine, cytidine, and guanosine. Thymidine is crucial for the replication and repair of DNA, playing a vital role in the cell cycle and cell division.

Structure

Thymidine consists of the base thymine linked to a deoxyribose sugar via a _-N1-glycosidic bond. The chemical formula of thymidine is C₁₀H₁₄N₂O₅. The deoxyribose sugar in thymidine lacks a hydroxyl group at the 2' position, distinguishing it from ribose found in RNA nucleosides.

Function

Thymidine is incorporated into DNA during the S phase of the cell cycle. It pairs with adenine through two hydrogen bonds, maintaining the stability of the DNA double helix. Thymidine is also involved in the DNA repair process, where it helps to replace damaged or mismatched bases.

Synthesis

Thymidine can be synthesized in cells through the salvage pathway or the de novo synthesis pathway. In the salvage pathway, thymidine is formed from thymine and deoxyribose-1-phosphate. In the de novo pathway, thymidine is synthesized from deoxyuridine monophosphate (dUMP) through the action of the enzyme thymidylate synthase.

Clinical Significance

Thymidine analogs, such as zidovudine (AZT), are used as antiretroviral drugs in the treatment of HIV/AIDS. These analogs interfere with viral DNA synthesis, inhibiting the replication of the virus. Thymidine is also used in thymidine labeling techniques to study cell proliferation.

Related pages

• DNA
• Nucleoside
• Thymine
• Deoxyribose
• Cell cycle