5-methylcytosine

from Wikipedia, the free encyclopedia
Structural formula
Structure of 5-methylcytosine
General
Surname 5-methylcytosine
other names

4-Amino-5-methyl-1 H -pyrimidin-2-one

Molecular formula C 5 H 7 N 3 O
Brief description

crystalline solid

External identifiers / databases
CAS number 554-01-8
EC number 209-058-3
ECHA InfoCard 100.008.236
PubChem 65040
ChemSpider 58551
Wikidata Q238563
properties
Molar mass 125.13 g mol −1
Physical state

firmly

Melting point

> 270 ° C

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

5-methylcytosine is a heterocyclic organic compound with a pyrimidine backbone. It is a derivative of the nucleic base cytosine with an additional methyl group in position 5. This substitution pattern corresponds to the analogy between uracil and thymine . 5-methylcytosine forms the nucleosides 5-methylcytidine  (5mC, m 5 C) in the RNA and 5-methyldeoxycytidine  ( 5-Me dC) in the DNA .

properties

Physical Properties

5-methylcytosine is a crystalline solid that melts at over 270 ° C.

Chemical properties

Due to its chemical instability, it can deaminate into thymine .

Deamination of 5-methylcytosine to thymine

Biological importance

In addition to 5-hydroxymethylcytosine , 5-formylcytosine and (still controversial) 5-carboxylcytosine, 5-methylcytosine is one of the modified DNA bases found in mammals. Therefore, 5-methylcytosine is often referred to as the fifth and 5-hydroxymethylcytosine is often referred to as the sixth base of DNA. 5-Methylcytosine is formed in vivo post- replicatively (after DNA synthesis) from cytosine by adding a methyl group ( DNA methylation ). This reaction is catalyzed by DNA methyl transferases (DNMTs).

Methylation of cytosine to 5-methylcytosine

5-methylcytosine plays an important role in epigenetics and is involved in switching genes on and off and probably also in the organization of DNA in chromosomes.

Under physiological conditions, a small part of the deoxycytidine contained in the DNA dehydrates to deoxyuridine , for which special repair systems exist in the cells. When 5-methyldeoxycytidine is deaminated , however, the deoxythymidine , which is also normally contained in the DNA, is produced , which cannot be recognized as faulty, which means that it can pair with deoxyadenosine in the next round of replication , which then results in a transition from deoxycytidine to deoxythymidine and on the opposite DNA strand from deoxyguanosine to deoxyadenosine.

literature

Individual evidence

  1. ↑ a b c data sheet 5-methylcytosine from AlfaAesar, accessed on February 7, 2011 ( PDF )(JavaScript required) .
  2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  3. ^ GA Wagner: Introduction to Archaeometry , 1st edition, Springer Verlag, Berlin 2007, ISBN 3-540-71936-9 , p. 282.
  4. ^ JR Siewert, M. Rothmund, V. Schumpelick: Praxis der Viszeralchirurgie: Onkologische Chirurgie , 3rd edition, Springer Verlag, Berlin 2010, ISBN 3-642-03807-7 , p. 71.
  5. ↑ Anja Naumann, Norbert Hochstein, Stefanie Weber, Walter Doerfler: “5-methylcytosine as an important regulator in genetics” (PDF file; 784 kB).
  6. ↑ Ralph Remus: Distribution of the fifth DNA base 5-methyl-deoxycytidine in the mammalian genome: DNA methylation patterns of endogenous retroviral sequences of the Syrian hamster (Mesocricetus auratus) and in the promoters of human erythrocyte membrane skeleton proteins (Homo sapiens) , dissertation 2000, University of Cologne ( PDF ) .

Web links

  • Entry for 5-methylcytosine in the Human Metabolome Database (HMDB) , accessed September 24, 2013.