Thymine

Thymine (C5H6N2O2) is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase.

Structure and properties

Thymine is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an oxygen atom at C4 and a methyl group at C5). The synthesis of thymine in organisms involves a series of enzyme-catalyzed reactions starting from uracil.

Function

Thymine combined with deoxyribose creates the nucleoside deoxythymidine, which is synonymous with the term thymidine. Thymidine can be phosphorylated with one, two, or three phosphoric acid groups, creating respectively, TMP, TDP or TTP (thymidine mono- di- or triphosphate).

Thymine in DNA

In DNA, thymine (T) binds to adenine (A) via two hydrogen bonds to assist in stabilizing the nucleic acid structures.

Thymine dimers

Thymine dimers are formed by a photochemical reaction from thymine. They are a primary cause of ultraviolet mutation, leading to melanomas.

See also

• Pyrimidine biosynthesis
• Nucleotide
• Base pair