CAS number 71-30-7 YesY
PubChem 597
ChemSpider 577 YesY
KEGG C00380 YesY
MeSH Cytosine
ChEBI CHEBI:16040 YesY
Jmol-3D images Image 1
Molecular formula C4H5N3O
Molar mass 111.10 g/mol
Density 1.55 g/cm3 (calculated)
Melting point

320-325 °C, 593-598 K, 608-617 °F (decomp.)

Acidity (pKa) 4.45 (secondary), 12.2 (primary)[1]
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Cytosine (C) is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). The nucleoside of cytosine is cytidine. In Watson-Crick base pairing, it forms three hydrogen bonds with guanine.



Cytosine was discovered by Albrecht Kossel in 1894 when it was hydrolysed from calf thymus tissues.[2] A structure was proposed in 1903, and was synthesized (and thus confirmed) in the laboratory in the same year.

Cytosine recently found use in quantum computation. The first time any quantum mechanical properties were harnessed to process information took place on August 1st in 1998 when researchers at Oxford implemented David Deutsch's algorithm on a two qubit NMRQC (Nuclear Magnetic Resonance Quantum Computer) based on the cytosine molecule.[3]

Chemical reactions

Cytosine with numbered components. Methylation occurs on carbon nr 5.

Cytosine can be found as part of DNA, as part of RNA, or as a part of a nucleotide. As cytidine triphosphate (CTP), it can act as a co-factor to enzymes, and can transfer a phosphate to convert adenosine diphosphate (ADP) to adenosine triphosphate (ATP).

In DNA and RNA, cytosine is paired with guanine. However, it is inherently unstable, and can change into uracil (spontaneous deamination). This can lead to a point mutation if not repaired by the DNA repair enzymes such as uracil glycosylase, which cleaves a uracil in DNA.

Cytosine can also be methylated into 5-methylcytosine by an enzyme called DNA methyltransferase or be methylated and hydroxylated to make 5-hydroxymethylcytosine. Active enzymatic deamination of cytosine or 5-methylcytosine by the APOBEC family of cytosine deaminases could have both beneficial and detrimental implications on various cellular processes as well as on organismal evolution.[4] The implications of deamination on 5-hydroxymethylcytosine, on the other hand, remains less understood.


  1. ^ Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
  2. ^ Kossel, A.; Steudel, H. Z. Physiol. Chem. 1903, 38, 49
  3. ^ Jones, J.A.; M. Mosca (1998-08-01). "Implementation of a quantum algorithm on a nuclear magnetic resonance quantum computer". J.Chem.Phys 109 (109): 1648–1653. doi:10.1063/1.476739. Retrieved 2007-10-18. 
  4. ^ Chahwan R., Wontakal S.N., and Roa S. (2010). "Crosstalk between genetic and epigenetic information through cytosine deamination". Trends in Genetics 26 (10): 443–448. doi:10.1016/j.tig.2010.07.005. PMID 20800313. 

External links

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Look at other dictionaries:

  • Cytosine — Structure de la 1H Cytosine Général …   Wikipédia en Français

  • cytosine — [ sitozin ] n. f. • 1903; de cyto et ine ♦ Biochim. Base pyrimidique présente dans l A. D. N. et dans l A. R. N. ● cytosine nom féminin Composé basique dérivé de la pyrimidine et constituant essentiel des acides nucléiques. (Elle est… …   Encyclopédie Universelle

  • cytosine — 1894, from Ger. cytosin (1894), from CYTO (Cf. cyto ) cell + ose + chemical suffix INE (Cf. ine) (2). The name cytosine (due to Kossel and Neumann) is misleading. Cytosine is not, like adenosine and guanosine, a nucleoside but the sugar free base …   Etymology dictionary

  • cytosine — cy to*sine (s[imac] t[ o]*s[i^]n or s[imac] t[ o]*s[=e]n), n. (Biochemistry) A pyrimidine ({C4H5N3O}) which is one of the four major basic components of DNA and RNA in most organisms, forming glyosides with ribose and deoxyribose. It is the basic …   The Collaborative International Dictionary of English

  • cytosine — cytosine. См. цитозин. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • cytosine — [sīt′ō sēn΄] n. [Ger zytosin < zyt , CYTO + os, OSE2 + in, INE3] a pyrimidine base, C4H5N3O, contained in the nucleic acids of all tissue: it links with guanine in the DNA structure …   English World dictionary

  • cytosine — /suy teuh seen , zeen , sin/, n. Biochem. a pyrimidine base, C4H5N3O, that is one of the fundamental components of DNA and RNA, in which it forms a base pair with guanine. Symbol: C Cf. cytidine, cytidine monophosphate. [ < G Cytosin (1894); see… …   Universalium

  • cytosine — citozinas statusas T sritis chemija formulė Formulę žr. priede. santrumpa( os) Cyt priedas( ai) Grafinis formatas atitikmenys: angl. cytosine rus. цитозин ryšiai: sinonimas – 4 amino 2 hidroksipirimidinas …   Chemijos terminų aiškinamasis žodynas

  • cytosine — citozinas statusas T sritis augalininkystė apibrėžtis Pirimidino bazė, įeinanti į DNR ir RNR sudėtį. atitikmenys: angl. cytosine rus. цитозин …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • cytosine — noun Etymology: International Scientific Vocabulary cyt + ose + 2 ine Date: 1894 a pyrimidine base C4H5N3O that codes genetic information in the polynucleotide chain of DNA or RNA compare adenine, guanine, thymine, uracil …   New Collegiate Dictionary