N/A - decomposes
Uracil is a common and naturally occurring pyrimidine derivative. Originally discovered in 1900, it was isolated by hydrolysis of yeast nuclein that was found in bovine thymus and spleen, herring sperm, and wheat germ. It is a planar, unsaturated compound that has the ability to absorb light.
Found in RNA, it 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 base-pair with any of the bases, depending on how the molecule arranges itself on the helix, but readily pairs with adenine because the methyl group is repelled into a fixed position. Uracil pairs with adenine through hydrogen bonding. Uracil is the hydrogen bond acceptor and can form two hydrogen bonds. Uracil can also bind with a ribose sugar to form the ribonucleoside uridine. When a phosphate attaches to uridine, uridine 5'-monophosphate is produced.
Uracil undergoes amide-imidic acid tautomeric shifts because any nuclear instability the molecule may have from the lack of formal aromaticity is compensated by the cyclic-amidic stability. The amide tautomer is referred to as the lactam structure, while the imidic acid tautomer is referred to as the lactim structure. These tautomeric forms are predominant at pH 7. The lactam structure is the most common form of uracil.
Uracil also recycles itself to form nucleotides by undergoing a series of phosphoribosyltransferase reactions. Degradation of uracil produces the substrates aspartate, carbon dioxide, and ammonia.
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