adenine

Adenine is a purine nucleobase with the chemical formula C5H5N5. It is a heterocyclic aromatic compound known as 6-aminopurine, consisting of a six-membered pyrimidine ring fused to a five-membered imidazole ring and bearing an amino group at position 6. In physiological conditions it behaves as a weak base and can be protonated under acidic conditions.

Adenine is one of the four nucleobases in DNA and RNA. In DNA, it pairs with thymine via two hydrogen bonds; in RNA, it pairs with uracil. This pairing is central to the encoding, replication, and transcription of genetic information. As a nucleobase, adenine is a component of nucleosides and nucleotides, existing as adenosine (adenine attached to ribose) and as AMP, ADP, and ATP (adenosine monophosphate, diphosphate, and triphosphate).

In metabolism, adenine is a building block of energy carriers and cofactors. ATP and ADP provide energy for countless cellular processes, while AMP participates in energy balance and signaling. The nucleotide form of adenine also appears in coenzymes and signaling molecules, and adenosine derivatives play roles in regulation of many physiological pathways. Adenine is synthesized de novo through purine biosynthesis and can be salvaged from degradation products via specific salvage enzymes to regenerate AMP.

Adenine is ubiquitous in living organisms and is essential for genetic information storage, energy transfer, and cellular signaling.