deoxynucleoside

A deoxynucleoside is a nucleoside in which the sugar component is deoxyribose rather than ribose. It consists of a purine or pyrimidine base attached to the 1′ carbon of the deoxyribose sugar via a β-N-glycosidic bond and lacks a phosphate group. The principal deoxynucleosides are deoxyadenosine (dA), deoxycytidine (dC), deoxyguanosine (dG), and thymidine (dT or dThd).

Compared with ribonucleosides, deoxynucleosides have a 2′-deoxyribose sugar, which lacks the 2′-hydroxyl group. This structural difference contributes to the greater chemical stability of DNA relative to RNA and underpins the role of deoxynucleosides in DNA rather than in RNA processes.

Biological role and metabolism: deoxynucleosides participate in the cellular salvage pathway, where they are phosphorylated by kinases to form deoxynucleoside monophosphates (dNMPs) and subsequently dNDPs and dNTPs, which are substrates for DNA synthesis. They are typically derived from DNA turnover or extracellular uptake and are essential for maintaining the pool of deoxynucleotide triphosphates used during replication and repair.

Applications: in molecular biology, deoxynucleosides and their nucleotide triphosphates are fundamental for DNA synthesis, sequencing, and various enzymatic reactions. In medicine, many antiviral and anticancer agents are deoxynucleoside analogs that disrupt DNA replication by acting as faulty substrates or chain terminators.