Uracil

Uracil is one of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U. The others are adenine, guanine, and cytosine. With the formula C4H4N2O2, uracil is a common and naturally occurring pyrimidine derivative.

Structure and properties

Uracil is a planar, unsaturated compound that has the ability to absorb light. The molecule can exist in several tautomeric forms, including the enol form (hydroxy-pyrimidinone), which is more stable in the solid phase and the keto form (oxy-pyrimidine), which is more stable in the solution phase.

Functions

In RNA, uracil base-pairs with adenine and replaces thymine during DNA transcription. Methylation of uracil produces thymine. It turns into thymine to protect the DNA and to improve the efficiency of DNA replication. Uracil can also be used for energy storage and transfer, as well as in the biosynthesis of the amino acids cysteine and methionine.

Synthesis

Uracil can be made from cytosine by spontaneous deamination. It can also be synthesized by a condensation reaction between malic acid and urea in the presence of heat.

Role in disease

Abnormalities in the enzymes that metabolize uracil have been associated with several human diseases, including cancer, neurodegenerative diseases, and congenital metabolic disorders.

See also

• Pyrimidine biosynthesis
• Nucleotide
• DNA
• RNA