Table of Contents
Introduction
Uracil is a pyrimidine nucleobase that is found only in RNAs. It is denoted by U or Ura. Demethylation of thymine yields uracil. It forms hydrogen bonds with adenine in a RNA polynucleotide chain. It is a natural and commonly occurring derivative of pyrimidine.
Uracil was first discovered by Alberto Ascoli by hydrolysing yeast nuclein in 1900. It can also be traced in bovine spleen and thymus, wheat germ and herring sperm. Previously in 1855, Robert Behrend coined the term uracil when he obtained traces of it while synthesising derivatives of uric acid.
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Fun Fact: In an analysis report of the Cassini mission, scientists have come to a conclusion that Titan, the biggest satellite of Saturn, may have uracil in its surface composition. |
Properties of Uracil
- It is an unsaturated and planar compound that can also absorb light.
- It is a weak acid and not much is known about its ionisation.
- Uracil produces urea and maleic acid upon oxidative degradation in the presence of hydrogen peroxide and ferrous ions.
- On degradation, uracil produces substrates such as carbon dioxide, aspartate and ammonia.
- Uracil forms base pairs with adenine in RNA strands. It gets replaced by thymine at the time of DNA transcription. The evolutionary replacement of thymine with uracil may have contributed towards the stability of DNA.
- It is a methylated form of thymine.
- Uracil forms hydrogen bonds with adenine, where it acts as both hydrogen bond donor and hydrogen bond acceptor.
- The nucleoside of uracil is known as uridine.
- It has two tautomeric forms: amide tautomer, known as lactam structure and imidic acid tautomer, known as lactim structure.
- Any nuclear instability that the uracil molecule may possess because of a lack of aromaticity is compensated by cyclic-amidic stability.
- Uracil readily undergoes alkylation, nitration and oxidation.
- It can be visualised under UV light in the presence of sodium hypochlorite and phenol.
- It can also react with elemental halogens because it possesses more than one electron donating group.
Synthesis of Uracil
Natural Synthesis
In 2009, NASA reported formation of Uracil from pyrimidine after exposure to UV light.
In 2105, life compounds such as uracil, thymine and cytosine were reported to have formed in outer space conditions by using polycyclic aromatic hydrocarbons as the starting material.
Laboratory Synthesis
Uracil can simply be produced in the laboratory by adding water to cytosine to produce uracil and ammonia.
Uracil is also produced by condensing malic acid in urea in the presence of fuming sulfuric acid.
Another way of uracil synthesis is by double decomposing thiouracil in an aqueous chloroacetic acid solution.
Lastly, photo dehydrogenation of 5,6-diuracil can also produce uracil.
Uses of Uracil
- Uracil helps in the synthesis of enzymes that are necessary for cell functioning.
- It also acts as a coenzyme and allosteric regulator for reactions in animals and plants.
- Uridine monophosphate (UMP) regulates the activity of aspartate transcarbamoylase and carbamoyl phosphate synthetase.
- UDP-glucose helps in the conversion of glucose to galactose in the liver.
- It also helps in the metabolism of carbohydrates.
- Uracil also takes part in the biosynthesis of polysaccharides and also transports aldehyde containing sugars.
- It is also important for detoxification of many carcinogens.
- It is also used in pharmaceuticals and drug delivery.
- The presence of uracil in tomatoes indicates the presence of lactic acid bacteria. Thus, it is used as a determinant for the contamination of tomatoes.
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