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thymine(thī`mēn), organic base of the pyrimidinepyrimidine
, type of organic base found in certain coenzymes and in the nucleic acids of plant and animal tissue. The three major pyrimidines of almost universal distribution in living systems are cytosine, thymine, and uracil.
..... Click the link for more information. family. Thymine was the first pyrimidine to be purified from a natural source, having been isolated from calf thymus and beef spleen in 1893–94. The accepted structure of the thymine molecule was published in 1900; this structure was confirmed when several investigators reported the synthesis of the compound during the period 1901 to 1910. Combined with the sugar deoxyribose in a glycosidic linkage, thymine forms a derivative called thymidine (a nucleoside), which in turn can be phosphorylated with from one to three phosphoric acid groups, yielding respectively the three nucleotidesnucleotide
, organic substance that serves as a monomer in forming nucleic acids. Nucleotides consist of either a purine or a pyrimidine base, a ribose or deoxyribose, and a phosphate group. Adenosine triphosphate serves as the principle energy carrier for the cell's reactions.
..... Click the link for more information. TMP (thymidine monophosphate), TDP (thymidine diphosphate), and TTP (thymidine triphosphate). The analogous nucleosides and nucleotides formed from thymine and ribose occur only very rarely in living systems; such is not the case with the other pyrimidines. The nucleotide derivatives of thymine do not exhibit as much activity as coenzymescoenzyme
, any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes. A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in
..... Click the link for more information. , although TTP can readily donate one of its phosphate groups to adenosine diphosphate (ADP) to form adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
..... Click the link for more information. (ATP), an extremely important intermediate in the transfer of chemical energy in living systems. Since the thymine nucleotides contain only deoxyribose and not ribose, TTP is the source of thymidine only in deoxyribonucleic acid (DNA); there is no thymine in ribonucleic acid (RNA). Thymidine is significant because of its involvement in the biosynthesis of DNA and in the preservation and transfer of genetic information. See nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
..... Click the link for more information. .
(5-methyluracil), a natural organic compound, a pyrimidine base. Thymine takes the form of white lamellar or acicular crystals that are readily soluble in hot water but poorly soluble in organic solvents.
Thymine is present in all organisms as a constituent of deoxyribonucleic acid (DNA) and several coenzymes of carbohydrate metabolism. It is also found in small quantities in transport ribonucleic
acid. It forms the nucleoside thymidine binding the carbohydrate deoxyribose. The synthetic analogue of thymidine, 5-bromouracil, is used in research as a powerful mutagen. By replacing thymine in the DNA chain, 5-bromouracil interferes with the correct formation of nucleotide pairs by the complementarity principle. This gives rise to errors in the replication of DNA and in the reading of the genetic code.