Deoxynucleotide

A deoxynucleotide is a nucleotide in which the sugar component is deoxyribose rather than ribose. In biology, the term most often refers to deoxyribonucleotides, the building blocks of DNA. They can exist as monophosphates, diphosphates, or triphosphates; the latter are the substrates used by DNA polymerases during replication and repair. The four standard deoxynucleotide triphosphates are dATP, dCTP, dGTP, and dTTP.

Each deoxynucleotide consists of a deoxyribose sugar attached to a nucleobase (adenine, cytosine, guanine, or thymine) and one to three phosphate groups.

In cells, ribonucleotide reductase reduces ribonucleotides to the corresponding deoxynucleotides, which are then phosphorylated by kinases to the diphosphates and triphosphates. Thymidylate synthase produces dTMP, which is further phosphorylated to dTTP. Deoxynucleotides can also be obtained by salvage pathways that recycle deoxynucleosides.

Maintaining balanced dNTP pools is essential for replication fidelity; imbalances can increase mutation rates and cause DNA damage. As substrates for DNA polymerases, their availability influences synthesis and repair; drugs that disrupt dNTP metabolism or mimic nucleotides are used as cancer therapies.