cytosine (sĪˈtōsēnˌ) [key], organic base of the pyrimidine family. It was isolated from the nucleic acid of calf thymus tissue in 1894. A suggested structure for cytosine, published in 1903, was confirmed in the same year when that base was synthesized in the laboratory. Combined with the sugar ribose in glycosidic linkage, cytosine forms a derivative called cytidine (a nucleoside), which in turn can be phosphorylated with from one to three phosphoric acid groups, yielding the three nucleotides CMP (cytidine monophosphate), CDP (cytidine diphosphate), and CTP (cytidine triphosphate). Analogous nucleosides and nucleotides are formed from cytosine and deoxyribose. The nucleoside derivatives of cytosine perform important functions in cellular metabolism. CTP acts as a coenzyme in both carbohydrate and lipid metabolism; it can readily donate one of its phosphate groups to adenosine diphosphate (ADP) to form adenosine triphosphate (ATP), an extremely important intermediate in the transfer of chemical energy in living systems. CTP is the source of the cytidine found in ribonucleic acid (RNA) and deoxycytidine triphosphate (dCTP) is the source of the deoxycytidine in deoxyribonucleic acid (DNA). Thus cytosine is intimately involved in the preservation and transfer of genetic information.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

More on cytosine from Fact Monster:

  • CMP - CMP CMP (cytidine monophosphate): see cytosine.
  • CDP - CDP CDP (cytidine diphosphate): see cytosine.
  • pyrimidine - pyrimidine pyrimidine , type of organic base found in certain coenzymes and in the nucleic acids of ...
  • nucleotide - nucleotide nucleotide , organic substance that serves as a monomer in forming nucleic acids. ...
  • nucleic acid: DNA - DNA The chemical and physical properties of DNA suit it for both replication and transfer of ...

See more Encyclopedia articles on: Biochemistry

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