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'''Uracil''' ({{IPAc-en|ˈ|j|ʊər|ə|s|ɪ|l}}) ([[nucleoside#List of nucleosides and corresponding nucleobases|symbol]] '''U''' or '''Ura''') is one of the four [[nucleobase]]s in the [[nucleic acid]] [[RNA]]. The others are [[adenine]] (A), [[cytosine]] (C), and [[guanine]] (G). In RNA, uracil binds to [[adenine]] via two [[Hydrogen bond|hydrogen bonds]]. In [[DNA]], the uracil nucleobase is replaced by [[thymine]] (T). Uracil is a [[demethylated]] form of [[thymine]].
'''Uracil''' ({{IPAc-en|ˈ|j|ʊər|ə|s|ɪ|l}}) ([[nucleoside#List of nucleosides and corresponding nucleobases|symbol]] '''U''' or '''Ura''') is one of the four [[nucleotide base]]s in the [[nucleic acid]] [[RNA]]. The others are [[adenine]] (A), [[cytosine]] (C), and [[guanine]] (G). In RNA, uracil binds to [[adenine]] via two [[hydrogen bond]]s. In [[DNA]], the uracil nucleobase is replaced by [[thymine]] (T). Uracil is a [[demethylated]] form of [[thymine]].


Uracil is a common and naturally occurring [[pyrimidine]] derivative.<ref name="Garrett1">{{cite book|title=Principles of Biochemistry with a Human Focus|vauthors=Garrett RH, Grisham CM|publisher=Brooks/Cole Thomson Learning|year=1997|location=United States}}</ref> The name "uracil" was coined in 1885 by the German chemist [[Robert Behrend]], who was attempting to synthesize derivatives of [[uric acid]].<ref>{{cite journal|vauthors=Behrend R|date=1885|title=Versuche zur Synthese von Körpern der Harnsäurereihe|trans-title=Experiments on the synthesis of substances in the uric acid series|url=http://babel.hathitrust.org/cgi/pt?id=mdp.39015026321698;view=1up;seq=11|journal=Annalen der Chemie|volume=229|issue=1–2|pages=1–44|doi=10.1002/jlac.18852290102|quote=Dasselbe stellt sich sonach als Methylderivat der Verbindung: welche ich willkürlich mit dem Namen Uracil belege, dar.|trans-quote=The same compound is therefore represented as the methyl derivative of the compound, which I will arbitrarily endow with the name ‘''uracil''’.}}</ref> Originally discovered in 1900 by [[Alberto Ascoli]], it was isolated by [[hydrolysis]] of [[yeast]] [[nuclein]];<ref>{{cite journal|vauthors=Ascoli A|date=1900|title=Über ein neues Spaltungsprodukt des Hefenucleins|trans-title=On a new cleavage product of nucleic acid from yeast|url=https://books.google.com/books?id=SXtNAAAAYAAJ&pg=PA161|journal=Zeitschrift für Physiologische Chemie|volume=31|issue=1–2|pages=161–164|doi=10.1515/bchm2.1901.31.1-2.161|archive-url=https://web.archive.org/web/20180512002431/https://books.google.com/books?id=SXtNAAAAYAAJ&pg=PA161|archive-date=12 May 2018}}</ref> it was also found in [[bovine]] [[thymus]] and [[spleen]], [[herring]] [[sperm]], and [[wheat]] [[Cereal germ|germ]].<ref name="brown1"/> It is a planar, unsaturated compound that has the ability to absorb light.<ref name="Horton1"/>
Uracil is a common and naturally occurring [[pyrimidine]] derivative.<ref name="Garrett1">{{cite book |title=Principles of Biochemistry with a Human Focus|vauthors=Garrett RH, Grisham CM |publisher=Brooks/Cole Thomson Learning |year=1997 |location=United States}}</ref> The name "uracil" was coined in 1885 by the German chemist [[Robert Behrend]], who was attempting to synthesize derivatives of [[uric acid]].<ref>{{cite journal |vauthors=Behrend R |date=1885 |title=Versuche zur Synthese von Körpern der Harnsäurereihe |trans-title=Experiments on the synthesis of substances in the uric acid series |url=http://babel.hathitrust.org/cgi/pt?id=mdp.39015026321698;view=1up;seq=11 |journal=Annalen der Chemie |volume=229 |issue=1–2|pages=1–44 |doi=10.1002/jlac.18852290102 |quote=Dasselbe stellt sich sonach als Methylderivat der Verbindung: welche ich willkürlich mit dem Namen Uracil belege, dar. |trans-quote=The same compound is therefore represented as the methyl derivative of the compound, which I will arbitrarily endow with the name ‘''uracil''’.}}</ref> Originally discovered in 1900 by [[Alberto Ascoli]], it was isolated by [[hydrolysis]] of [[yeast]] [[nuclein]];<ref>{{cite journal|vauthors=Ascoli A|date=1900|title=Über ein neues Spaltungsprodukt des Hefenucleins|trans-title=On a new cleavage product of nucleic acid from yeast|url=https://books.google.com/books?id=SXtNAAAAYAAJ&pg=PA161|journal=Zeitschrift für Physiologische Chemie|volume=31|issue=1–2|pages=161–164|doi=10.1515/bchm2.1901.31.1-2.161|archive-url=https://web.archive.org/web/20180512002431/https://books.google.com/books?id=SXtNAAAAYAAJ&pg=PA161|archive-date=12 May 2018}}</ref> it was also found in [[bovine]] [[thymus]] and [[spleen]], [[herring]] [[sperm]], and [[wheat]] [[Cereal germ|germ]].<ref name="brown1"/> It is a planar, unsaturated compound that has the ability to absorb light.<ref name="Horton1"/>


Uracil that was formed extraterrestrially has been detected in the [[Murchison meteorite]],<ref name="Murch_base" /> in [[near-Earth asteroid]] [[162173 Ryugu|Ryugu]],<ref name="Oba 2023" /> and possibly on the surface of the moon [[Titan (moon)|Titan]].<ref name="Clark 2012"/> It has been synthesized under cold laboratory conditions similar to outer space, from pyrimidine embedded in water ice and exposed to ultraviolet light.<ref name="Nuevo 2009" />
Based on <sup>12</sup>C/<sup>13</sup>C [[isotopic ratio]]s of [[organic compounds]] found in the [[Murchison meteorite]], it is believed that uracil, [[xanthine]], and related molecules can also be formed extraterrestrially.<ref name="Murch_base">{{cite journal|display-authors=6|vauthors=Martins Z, Botta O, Fogel ML, Sephton MA, Glavin DP, Watson JS, Dworkin JP, Schwartz AW, Ehrenfreund P|date=2008|title=Extraterrestrial nucleobases in the Murchison meteorite|journal=[[Earth and Planetary Science Letters]]|volume=270|issue=1–2|pages=130–136|arxiv=0806.2286|bibcode=2008E&PSL.270..130M|doi=10.1016/j.epsl.2008.03.026|s2cid=14309508}}</ref><ref>{{cite web|url=http://afp.google.com/article/ALeqM5j_QHxWNRNdiW35Qr00L8CkwcXyvw|title=We may all be space aliens: Study|date=20 Aug 2009|website=[[Agence France-Presse|AFP]]|url-status=live|archive-url=https://web.archive.org/web/20080617213441/http://afp.google.com/article/ALeqM5j_QHxWNRNdiW35Qr00L8CkwcXyvw|archive-date=17 June 2008|access-date=14 Aug 2011}}</ref> Data from the [[Cassini mission]], orbiting in the [[Saturn]] system, suggests that uracil is present in the surface of the moon [[Titan (moon)|Titan]].<ref>{{cite journal|display-authors=6|vauthors=Clark RN, Pearson N, Brown RH, Cruikshank DP, Barnes J, Jaumann R, Soderblom L, Griffith C, Rannou P, Rodriguez S, Le Mouelic S, Lunine J, Sotin C, Baines KH, Buratti BJ, Nicholson PD, Nelson RM, Stephan K|date=2012|title=The Surface Composition of Titan|journal=American Astronomical Society|volume=44|pages=201.02|bibcode=2012DPS....4420102C}}</ref> In March 2023, Japanese researchers announced that they detected uracil in a sample collected from [[162173 Ryugu]], a near-Earth asteroid.<ref>{{cite journal | vauthors = Oba Y, Koga T, Takano Y, Ogawa NO, Ohkouchi N, Sasaki K, Sato H, Glavin DP, Dworkin JP, Naraoka H, Tachibana S, Yurimoto H, Nakamura T, Noguchi T, Okazaki R, Yabuta H, Sakamoto K, Yada T, Nishimura M, Nakato A, Miyazaki A, Yogata K, Abe M, Okada T, Usui T, Yoshikawa M, Saiki T, Tanaka S, Terui F, Nakazawa S, Watanabe SI, Tsuda Y | display-authors = 6 | title = Uracil in the carbonaceous asteroid (162173) Ryugu | journal = Nature Communications | volume = 14 | issue = 1 | pages = 1292 | date = March 2023 | pmid = 36944653 | doi = 10.1038/s41467-023-36904-3 }}</ref><ref>{{Cite news | vauthors = Dunham W |date=2023-03-21 |title=Asteroid discovery suggests ingredients for life on Earth came from space |language=en |work=Reuters |url=https://www.reuters.com/lifestyle/science/asteroid-discovery-suggests-ingredients-life-earth-came-space-2023-03-21/ |access-date=2023-03-21}}</ref>


==Properties==
==Properties==
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Oxidative degradation of uracil produces urea and maleic acid in the presence of [[hydrogen peroxide|H<sub>2</sub>O<sub>2</sub>]] and [[Iron|Fe]]<sup>2+</sup> or in the presence of diatomic [[oxygen]] and Fe<sup>2+</sup>.
Oxidative degradation of uracil produces urea and maleic acid in the presence of [[hydrogen peroxide|H<sub>2</sub>O<sub>2</sub>]] and [[Iron|Fe]]<sup>2+</sup> or in the presence of diatomic [[oxygen]] and Fe<sup>2+</sup>.


Uracil is a [[weak acid]]. The first site of [[ionization]] of uracil is not known.<ref name="Zorbach1">{{cite book|title=Synthetic Procedures in Nucleic Acid Chemistry: Physical and physicochemical aids in determination of structure|vauthors=Zorbach WW, Tipson RS|publisher=Wiley-Interscience|year=1973|isbn=9780471984184|volume=2|location=New York, NY}}</ref> The negative charge is placed on the oxygen anion and produces a [[Acid dissociation constant|p''K''<sub>a</sub>]] of less than or equal to 12. The basic p''K''<sub>a</sub>&nbsp;=&nbsp;−3.4, while the acidic p''K''<sub>a</sub>&nbsp;=&nbsp;9.38<sub>9</sub>. In the gas phase, uracil has four sites that are more acidic than water.<ref name="Lee1">{{cite journal | vauthors = Kurinovich MA, Lee JK | title = The acidity of uracil and uracil analogs in the gas phase: four surprisingly acidic sites and biological implications | journal = Journal of the American Society for Mass Spectrometry | volume = 13 | issue = 8 | pages = 985–995 | date = August 2002 | pmid = 12216739 | doi = 10.1016/S1044-0305(02)00410-5 | doi-access = free }}</ref>
Uracil is a [[weak acid]]. The first site of [[ionization]] of uracil is not known.<ref name="Zorbach1">{{cite book|title=Synthetic Procedures in Nucleic Acid Chemistry: Physical and physicochemical aids in determination of structure|vauthors=Zorbach WW, Tipson RS|publisher=Wiley-Interscience|year=1973|isbn=9780471984184|volume=2|location=New York, NY}}</ref> The negative charge is placed on the oxygen anion and produces a [[Acid dissociation constant|p''K''<sub>a</sub>]] of less than or equal to 12. The basic p''K''<sub>a</sub>&nbsp;=&nbsp;−3.4, while the acidic p''K''<sub>a</sub>&nbsp;=&nbsp;9.38<sub>9</sub>. In the gas phase, uracil has four sites that are more acidic than water.<ref name="Lee1">{{cite journal | vauthors = Kurinovich MA, Lee JK | title = The acidity of uracil and uracil analogs in the gas phase: four surprisingly acidic sites and biological implications | journal = Journal of the American Society for Mass Spectrometry | volume = 13 | issue = 8 | pages = 985–995 | date = August 2002 | pmid = 12216739 | doi = 10.1016/S1044-0305(02)00410-5 | doi-access = free | bibcode = 2002JASMS..13..985K }}</ref>


===In DNA===
===In DNA===
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[[Uracil-DNA glycosylase]] excises uracil bases from double-stranded DNA. This enzyme would therefore recognize and cut out both types of uracil – the one incorporated naturally, and the one formed due to cytosine deamination, which would trigger unnecessary and inappropriate repair processes.<ref>{{Cite journal|vauthors=Békési A, Vértessy BG|date=2011|title=Uracil in DNA: error or signal?|url=https://www.scienceinschool.org/2011/issue18/uracil|journal=Science in School|pages=18|archive-url=https://web.archive.org/web/20160323021752/http://www.scienceinschool.org/2011/issue18/uracil|archive-date=23 March 2016}}</ref>
[[Uracil-DNA glycosylase]] excises uracil bases from double-stranded DNA. This enzyme would therefore recognize and cut out both types of uracil – the one incorporated naturally, and the one formed due to cytosine deamination, which would trigger unnecessary and inappropriate repair processes.<ref>{{Cite journal|vauthors=Békési A, Vértessy BG|date=2011|title=Uracil in DNA: error or signal?|url=https://www.scienceinschool.org/2011/issue18/uracil|journal=Science in School|pages=18|archive-url=https://web.archive.org/web/20160323021752/http://www.scienceinschool.org/2011/issue18/uracil|archive-date=23 March 2016}}</ref>


This problem is believed to have been solved in terms of evolution, that is by "tagging" (methylating) uracil. Methylated uracil is identical to thymine. Hence the hypothesis that, over time, thymine became standard in DNA instead of uracil. So cells continue to use uracil in RNA, and not in DNA, because RNA is shorter-lived than DNA, and any potential uracil-related errors do not lead to lasting damage. Apparently, either there was no evolutionary pressure to replace uracil in RNA with the more complex thymine, or uracil has some chemical property that is useful in RNA, which thymine lacks. Uracil-containing DNA still exists, for example in
This problem is believed to have been solved in terms of evolution, that is by "tagging" (methylating) uracil. Methylated uracil is identical to thymine. Hence the hypothesis that, over time, thymine became standard in DNA instead of uracil. So cells continue to use uracil in RNA, and not in DNA, because RNA is shorter-lived than DNA, and any potential uracil-related errors do not lead to lasting damage. Apparently, either there was no evolutionary pressure to replace uracil in RNA with the more complex thymine, or uracil has some chemical property that is useful in RNA, which thymine lacks. Uracil-containing DNA still exists, for example in:
* DNA of several [[phage]]s<ref>{{cite journal | vauthors = Wang Z, Mosbaugh DW | title = Uracil-DNA glycosylase inhibitor of bacteriophage PBS2: cloning and effects of expression of the inhibitor gene in Escherichia coli | journal = Journal of Bacteriology | volume = 170 | issue = 3 | pages = 1082–1091 | date = March 1988 | pmid = 2963806 | pmc = 210877 | doi = 10.1128/JB.170.3.1082-1091.1988 }}</ref>
* DNA of several [[phage]]s<ref>{{cite journal | vauthors = Wang Z, Mosbaugh DW | title = Uracil-DNA glycosylase inhibitor of bacteriophage PBS2: cloning and effects of expression of the inhibitor gene in Escherichia coli | journal = Journal of Bacteriology | volume = 170 | issue = 3 | pages = 1082–1091 | date = March 1988 | pmid = 2963806 | pmc = 210877 | doi = 10.1128/JB.170.3.1082-1091.1988 }}</ref>
* [[Endopterygote]] development
* [[Endopterygote]] development
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===Biological===
===Biological===
{{See also|Pyrimidine metabolism}}
{{See also|Pyrimidine metabolism}}
Organisms synthesize uracil, in the form of [[uridine monophosphate]] (UMP), by decarboxylating [[orotidine 5'-monophosphate]] (orotidylic acid). In humans this decarboxylation is achieved by the enzyme [[Uridine monophosphate synthase|UMP synthase]]. In contrast to the purine nucleotides, the pyrimidine ring (orotidylic acid) that leads uracil is synthesized first and then linked to [[ribose phosphate]], forming UMP.<ref name="Loffler 2004">{{cite book | last=Löffler | first=Monika | last2=Zameitat | first2=Elke | title=Encyclopedia of Biological Chemistry | chapter=Pyrimidine Biosynthesis | publisher=Elsevier | year=2004 | doi=10.1016/b0-12-443710-9/00574-3 | pages=600–605}}</ref>
Organisms synthesize uracil, in the form of [[uridine monophosphate]] (UMP), by decarboxylating [[orotidine 5'-monophosphate]] (orotidylic acid). In humans this decarboxylation is achieved by the enzyme [[Uridine monophosphate synthase|UMP synthase]]. In contrast to the purine nucleotides, the pyrimidine ring (orotidylic acid) that leads uracil is synthesized first and then linked to [[ribose phosphate]], forming UMP.<ref name="Loffler 2004">{{cite book | last1=Löffler | first1=Monika | last2=Zameitat | first2=Elke | title=Encyclopedia of Biological Chemistry | chapter=Pyrimidine Biosynthesis | publisher=Elsevier | year=2004 | doi=10.1016/b0-12-443710-9/00574-3 | pages=600–605| isbn=9780124437104 }}</ref>


===Laboratory===
===Laboratory===
There are many laboratory [[Chemical synthesis|syntheses]] of uracil available. The first reaction is the simplest of the syntheses, by adding water to [[cytosine]] to produce uracil and [[ammonia]]:<ref name = "Garrett1"/>
There are many laboratory [[Chemical synthesis|synthesis]] of uracil available. The first reaction is the simplest of the syntheses, by adding water to [[cytosine]] to produce uracil and [[ammonia]]:<ref name = "Garrett1"/>
:{{chem2|C4H5N3O}} + {{chem2|H2O}} → {{chem2|C4H4N2O2}} + {{chem2|NH3}}
:{{chem2|C4H5N3O}} + {{chem2|H2O}} → {{chem2|C4H4N2O2}} + {{chem2|NH3}}


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===Prebiotic===
===Prebiotic===
In 2009, [[NASA]] scientists reported having produced uracil from [[pyrimidine]] and water ice by exposing it to [[ultraviolet light]] under space-like conditions. This suggests a possible natural original source for uracil.<ref name="NASA-20091105">{{cite news| vauthors = Marlaire R |url= http://www.nasa.gov/centers/ames/news/features/2009/urasil.html |title=NASA reproduces a building block of life in laboratory|date=5 November 2009 |access-date=5 March 2015|url-status=live |archive-url=https://web.archive.org/web/20160304234115/http://www.nasa.gov/centers/ames/news/features/2009/urasil.html |archive-date=4 March 2016 |publisher=[[NASA]] }}</ref> More recently, in March 2015, NASA scientists reported that additional complex [[DNA]] and [[RNA]] [[organic compound]]s of [[life]], including uracil, [[cytosine]] and [[thymine]], have been formed in the laboratory under [[outer space]] conditions, using starting chemicals, such as [[pyrimidine]], found in [[meteorite]]s. Pyrimidine, like [[polycyclic aromatic hydrocarbons]] (PAHs), the most carbon-rich chemical found in the [[Universe]], may have been formed in [[red giant]]s or in [[Cosmic dust|interstellar dust]] and gas clouds, according to the scientists.<ref name="NASA-20150303">{{cite news| vauthors = Marlaire R |url= http://www.nasa.gov/content/nasa-ames-reproduces-the-building-blocks-of-life-in-laboratory|title=NASA Ames reproduces the building blocks of life in laboratory|date=3 Mar 2015|access-date=5 Mar 2015|url-status=live|archive-url=https://web.archive.org/web/20150305083306/http://www.nasa.gov/content/nasa-ames-reproduces-the-building-blocks-of-life-in-laboratory/|archive-date=5 March 2015|publisher=[[NASA]]}}</ref>
In 2009, [[NASA]] scientists reported having produced uracil from [[pyrimidine]] and water ice by exposing it to [[ultraviolet light]] under space-like conditions.<ref name="Nuevo 2009">{{cite journal | last1=Nuevo | first1=Michel | last2=Milam | first2=Stefanie N. | last3=Sandford | first3=Scott A. | last4=Elsila | first4=Jamie E. | last5=Dworkin | first5=Jason P. | title=Formation of Uracil from the Ultraviolet Photo-Irradiation of Pyrimidine in Pure H2O Ices | journal=Astrobiology | volume=9 | issue=7 | year=2009 | issn=1531-1074 | doi=10.1089/ast.2008.0324 | pages=683–695| pmid=19778279 | bibcode=2009AsBio...9..683N }}</ref> This suggests a possible natural original source for uracil.<ref name="NASA-20091105">{{cite news| vauthors = Marlaire R |url= http://www.nasa.gov/centers/ames/news/features/2009/urasil.html |title=NASA reproduces a building block of life in laboratory|date=5 November 2009 |access-date=5 March 2015|url-status=live |archive-url=https://web.archive.org/web/20160304234115/http://www.nasa.gov/centers/ames/news/features/2009/urasil.html |archive-date=4 March 2016 |publisher=[[NASA]] }}</ref> In 2014, NASA scientists reported that additional complex [[DNA]] and [[RNA]] [[organic compound]]s of [[life]], including uracil, [[cytosine]] and [[thymine]], have been formed in the laboratory under [[outer space]] conditions, starting with ice, [[pyrimidine]], ammonia, and methanol, which are compounds found in astrophysical environments.<ref name="Nuevo 2014">{{cite journal | last1=Nuevo | first1=Michel | last2=Materese | first2=Christopher K. | last3=Sandford | first3=Scott A. | title=The Photochemistry of Pyrimidine in Realistic Astrophysical ICES and the Production of Nucleobases | journal=The Astrophysical Journal | volume=793 | issue=2 | date=2014| issn=1538-4357 | doi=10.1088/0004-637x/793/2/125 | page=125| bibcode=2014ApJ...793..125N | s2cid=54189201 }}</ref> Pyrimidine, like [[polycyclic aromatic hydrocarbons]] (PAHs), a carbon-rich chemical found in the [[Universe]], may have been formed in [[red giant]]s or in [[Cosmic dust|interstellar dust]] and gas clouds.<ref name="NASA-20150303">{{cite news| vauthors = Marlaire R |url= http://www.nasa.gov/content/nasa-ames-reproduces-the-building-blocks-of-life-in-laboratory|title=NASA Ames reproduces the building blocks of life in laboratory|date=3 Mar 2015|access-date=5 Mar 2015|url-status=live|archive-url=https://web.archive.org/web/20150305083306/http://www.nasa.gov/content/nasa-ames-reproduces-the-building-blocks-of-life-in-laboratory/|archive-date=5 March 2015|publisher=[[NASA]]}}</ref>


In 2023, uracil was observed in a sample from a [[Near-earth asteroid|near-Earth asteroid]] with no exposure to Earth's biosphere, giving further evidence for synthesis in space.<ref>{{cite journal | vauthors = Oba Y, Koga T, Takano Y, Ogawa NO, Ohkouchi N, Sasaki K, Sato H, Glavin DP, Dworkin JP, Naraoka H, Tachibana S, Yurimoto H, Nakamura T, Noguchi T, Okazaki R, Yabuta H, Sakamoto K, Yada T, Nishimura M, Nakato A, Miyazaki A, Yogata K, Abe M, Okada T, Usui T, Yoshikawa M, Saiki T, Tanaka S, Terui F, Nakazawa S, Watanabe SI, Tsuda Y | display-authors = 6 | title = Uracil in the carbonaceous asteroid (162173) Ryugu | journal = Nature Communications | volume = 14 | issue = 1 | pages = 1292 | date = March 2023 | pmid = 36944653 | pmc = 10030641 | doi = 10.1038/s41467-023-36904-3 }}</ref>
Based on <sup>12</sup>C/<sup>13</sup>C [[isotopic ratio]]s of [[organic compounds]] found in the [[Murchison meteorite]], it is believed that uracil, [[xanthine]], and related molecules can also be formed extraterrestrially.<ref name="Murch_base">{{cite journal|display-authors=6|vauthors=Martins Z, Botta O, Fogel ML, Sephton MA, Glavin DP, Watson JS, Dworkin JP, Schwartz AW, Ehrenfreund P|date=2008|title=Extraterrestrial nucleobases in the Murchison meteorite|journal=[[Earth and Planetary Science Letters]]|volume=270|issue=1–2|pages=130–136|arxiv=0806.2286|bibcode=2008E&PSL.270..130M|doi=10.1016/j.epsl.2008.03.026|s2cid=14309508}}</ref> Data from the [[Cassini mission]], orbiting in the [[Saturn]] system, suggests that uracil is present in the surface of the moon [[Titan (moon)|Titan]].<ref name="Clark 2012">{{cite journal|display-authors=6|vauthors=Clark RN, Pearson N, Brown RH, Cruikshank DP, Barnes J, Jaumann R, Soderblom L, Griffith C, Rannou P, Rodriguez S, Le Mouelic S, Lunine J, Sotin C, Baines KH, Buratti BJ, Nicholson PD, Nelson RM, Stephan K|date=2012|title=The Surface Composition of Titan|journal=American Astronomical Society|volume=44|pages=201.02|bibcode=2012DPS....4420102C}}</ref> In 2023, uracil was observed in a sample from [[162173 Ryugu]], a [[near-Earth asteroid]], with no exposure to Earth's biosphere, giving further evidence for synthesis in space.<ref name="Oba 2023">{{cite journal | vauthors = Oba Y, Koga T, Takano Y, Ogawa NO, Ohkouchi N, Sasaki K, Sato H, Glavin DP, Dworkin JP, Naraoka H, Tachibana S, Yurimoto H, Nakamura T, Noguchi T, Okazaki R, Yabuta H, Sakamoto K, Yada T, Nishimura M, Nakato A, Miyazaki A, Yogata K, Abe M, Okada T, Usui T, Yoshikawa M, Saiki T, Tanaka S, Terui F, Nakazawa S, Watanabe SI, Tsuda Y | display-authors = 6 | title = Uracil in the carbonaceous asteroid (162173) Ryugu | journal = Nature Communications | volume = 14 | issue = 1 | pages = 1292 | date = 2023 | pmid = 36944653 | pmc = 10030641 | doi = 10.1038/s41467-023-36904-3 | bibcode = 2023NatCo..14.1292O }}</ref>


==Reactions==
==Reactions==
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==Uses==
==Uses==
Uracil's use in the body is to help carry out the synthesis of many enzymes necessary for cell function through bonding with riboses and phosphates.<ref name="Garrett1"/> Uracil serves as [[allosteric]] regulator and [[coenzyme]] for reactions in animals and in plants.<ref name = "Brown2"/> UMP controls the activity of [[carbamoyl phosphate synthetase]] and [[aspartate transcarbamoylase]] in plants, while UDP and UTP regulate [[CPSase II]] activity in [[animal]]s. UDP-glucose regulates the conversion of [[glucose]] to [[galactose]] in the [[liver]] and other tissues in the process of [[carbohydrate metabolism]].<ref name="Brown2"/> Uracil is also involved in the [[biosynthesis]] of [[polysaccharides]] and the transportation of sugars containing [[aldehydes]].<ref name="Brown2">{{cite book|title=Ring Nitrogen and Key Biomolecules: The biochemistry of ''N''-heterocycles|publisher=Lluwer Academic Publishers|year=1998|isbn=9780412835704|veditors=Brown EG|location=Boston, MA|doi=10.1007/978-94-011-4906-8| vauthors = Brown EG |s2cid=9708198}}</ref> Uracil is important for the detoxification of many [[carcinogen|carcinogens]], for instance those found in tobacco smoke.<ref name="Olson">{{cite journal | vauthors = Olson KC, Sun D, Chen G, Sharma AK, Amin S, Ropson IJ, Spratt TE, Lazarus P | display-authors = 6 | title = Characterization of dibenzo[a,l]pyrene-trans-11,12-diol (dibenzo[def,p]chrysene) glucuronidation by UDP-glucuronosyltransferases | journal = Chemical Research in Toxicology | volume = 24 | issue = 9 | pages = 1549–1559 | date = September 2011 | pmid = 21780761 | pmc = 3177992 | doi = 10.1021/tx200178v }}</ref> Uracil is also required to detoxify many drugs such as cannabinoids (THC)<ref name="Mazur">{{cite journal | vauthors = Mazur A, Lichti CF, Prather PL, Zielinska AK, Bratton SM, Gallus-Zawada A, Finel M, Miller GP, Radomińska-Pandya A, Moran JH | display-authors = 6 | title = Characterization of human hepatic and extrahepatic UDP-glucuronosyltransferase enzymes involved in the metabolism of classic cannabinoids | journal = Drug Metabolism and Disposition | volume = 37 | issue = 7 | pages = 1496–1504 | date = July 2009 | pmid = 19339377 | pmc = 2698943 | doi = 10.1124/dmd.109.026898 }}</ref> and morphine (opioids).<ref name="DeGregori">{{cite journal | vauthors = De Gregori S, De Gregori M, Ranzani GN, Allegri M, Minella C, Regazzi M | title = Morphine metabolism, transport and brain disposition | journal = Metabolic Brain Disease | volume = 27 | issue = 1 | pages = 1–5 | date = March 2012 | pmid = 22193538 | pmc = 3276770 | doi = 10.1007/s11011-011-9274-6 }}</ref> It can also slightly increase the risk for cancer in unusual cases in which the body is extremely deficient in [[folate]].<ref name = "Mashiyama1"/> The deficiency in folate leads to increased ratio of [[Deoxyuridine monophosphate|deoxyuridine monophosphates]] (dUMP)/[[Deoxythymidine monophosphate|deoxythymidine monophosphates]] (dTMP) and uracil misincorporation into DNA and eventually low production of DNA.<ref name="Mashiyama1">{{cite journal | vauthors = Mashiyama ST, Courtemanche C, Elson-Schwab I, Crott J, Lee BL, Ong CN, Fenech M, Ames BN | display-authors = 6 | title = Uracil in DNA, determined by an improved assay, is increased when deoxynucleosides are added to folate-deficient cultured human lymphocytes | journal = Analytical Biochemistry | volume = 330 | issue = 1 | pages = 58–69 | date = July 2004 | pmid = 15183762 | doi = 10.1016/j.ab.2004.03.065 }}</ref>
Uracil's use in the body is to help carry out the synthesis of many enzymes necessary for cell function through bonding with riboses and phosphates.<ref name="Garrett1"/> Uracil serves as [[allosteric]] regulator and [[coenzyme]] for reactions in animals and in plants.<ref name = "Brown2"/> UMP controls the activity of [[carbamoyl phosphate synthetase]] and [[aspartate transcarbamoylase]] in plants, while UDP and UTP regulate [[CPSase II]] activity in [[animal]]s. UDP-glucose regulates the conversion of [[glucose]] to [[galactose]] in the [[liver]] and other tissues in the process of [[carbohydrate metabolism]].<ref name="Brown2"/> Uracil is also involved in the [[biosynthesis]] of [[polysaccharides]] and the transportation of sugars containing [[aldehydes]].<ref name="Brown2">{{cite book|title=Ring Nitrogen and Key Biomolecules: The biochemistry of ''N''-heterocycles|publisher=Lluwer Academic Publishers|year=1998|isbn=9780412835704|veditors=Brown EG|location=Boston, MA|doi=10.1007/978-94-011-4906-8| vauthors = Brown EG |s2cid=9708198}}</ref> Uracil is important for the detoxification of many [[carcinogen]]s, for instance those found in tobacco smoke.<ref name="Olson">{{cite journal | vauthors = Olson KC, Sun D, Chen G, Sharma AK, Amin S, Ropson IJ, Spratt TE, Lazarus P | display-authors = 6 | title = Characterization of dibenzo[a,l]pyrene-trans-11,12-diol (dibenzo[def,p]chrysene) glucuronidation by UDP-glucuronosyltransferases | journal = Chemical Research in Toxicology | volume = 24 | issue = 9 | pages = 1549–1559 | date = September 2011 | pmid = 21780761 | pmc = 3177992 | doi = 10.1021/tx200178v }}</ref> Uracil is also required to detoxify many drugs such as cannabinoids (THC)<ref name="Mazur">{{cite journal | vauthors = Mazur A, Lichti CF, Prather PL, Zielinska AK, Bratton SM, Gallus-Zawada A, Finel M, Miller GP, Radomińska-Pandya A, Moran JH | display-authors = 6 | title = Characterization of human hepatic and extrahepatic UDP-glucuronosyltransferase enzymes involved in the metabolism of classic cannabinoids | journal = Drug Metabolism and Disposition | volume = 37 | issue = 7 | pages = 1496–1504 | date = July 2009 | pmid = 19339377 | pmc = 2698943 | doi = 10.1124/dmd.109.026898 }}</ref> and morphine (opioids).<ref name="DeGregori">{{cite journal | vauthors = De Gregori S, De Gregori M, Ranzani GN, Allegri M, Minella C, Regazzi M | title = Morphine metabolism, transport and brain disposition | journal = Metabolic Brain Disease | volume = 27 | issue = 1 | pages = 1–5 | date = March 2012 | pmid = 22193538 | pmc = 3276770 | doi = 10.1007/s11011-011-9274-6 }}</ref> It can also slightly increase the risk for cancer in unusual cases in which the body is extremely deficient in [[folate]].<ref name = "Mashiyama1"/> The deficiency in folate leads to increased ratio of [[deoxyuridine monophosphate]]s (dUMP)/[[deoxythymidine monophosphate]]s (dTMP) and uracil misincorporation into DNA and eventually low production of DNA.<ref name="Mashiyama1">{{cite journal | vauthors = Mashiyama ST, Courtemanche C, Elson-Schwab I, Crott J, Lee BL, Ong CN, Fenech M, Ames BN | display-authors = 6 | title = Uracil in DNA, determined by an improved assay, is increased when deoxynucleosides are added to folate-deficient cultured human lymphocytes | journal = Analytical Biochemistry | volume = 330 | issue = 1 | pages = 58–69 | date = July 2004 | pmid = 15183762 | doi = 10.1016/j.ab.2004.03.065 }}</ref>


Uracil can be used for [[drug delivery]] and as a [[pharmaceutical]]. When elemental [[fluorine]] reacts with uracil, they produce [[5-fluorouracil]]. 5-Fluorouracil is an anticancer drug ([[antimetabolite]]) used to masquerade as uracil during the nucleic acid replication process.<ref name="Garrett1"/> Because 5-fluorouracil is similar in shape to, but does not undergo the same chemistry as, uracil, the drug inhibits [[RNA]] transcription enzymes, thereby blocking RNA synthesis and stopping the growth of cancerous cells.<ref name="Garrett1"/> Uracil can also be used in the synthesis of caffeine.<ref>{{cite journal|vauthors=Zajac MA, Zakrzewski AG, Kowal MG, Narayan S|date=2003|title=A novel method of caffeine synthesis from uracil|journal=Synthetic Communications|volume=33|issue=19|pages=3291–3297|doi=10.1081/SCC-120023986|s2cid=43220488}}</ref> Uracil has also shown potential as a HIV viral capsid inhibitor.<ref>{{cite journal | vauthors = Ramesh D, Mohanty AK, De A, Vijayakumar BG, Sethumadhavan A, Muthuvel SK, Mani M, Kannan T | display-authors = 6 | title = Uracil derivatives as HIV-1 capsid protein inhibitors: design, <i>in silico</i>, <i>in vitro</i> and cytotoxicity studies | journal = RSC Advances | volume = 12 | issue = 27 | pages = 17466–17480 | date = June 2022 | pmid = 35765450 | pmc = 9190787 | doi = 10.1039/D2RA02450K | bibcode = 2022RSCAd..1217466R }}</ref> Uracil derivatives have anti-tubercular and anti-leishmanial activity.<ref>{{cite journal | vauthors = Ramesh D, Sarkar D, Joji A, Singh M, Mohanty AK, G Vijayakumar B, Chatterjee M, Sriram D, Muthuvel SK, Kannan T | display-authors = 6 | title = First-in-class pyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones against leishmaniasis and tuberculosis: Rationale, in vitro, ex vivo studies and mechanistic insights | journal = Archiv Der Pharmazie | volume = 355 | issue = 4 | pages = e2100440 | date = April 2022 | pmid = 35106845 | doi = 10.1002/ardp.202100440 | s2cid = 246474821 }}</ref>
Uracil can be used for [[drug delivery]] and as a [[pharmaceutical]]. When elemental [[fluorine]] reacts with uracil, they produce [[5-fluorouracil]]. 5-Fluorouracil is an anticancer drug ([[antimetabolite]]) used to masquerade as uracil during the nucleic acid replication process.<ref name="Garrett1"/> Because 5-fluorouracil is similar in shape to, but does not undergo the same chemistry as, uracil, the drug inhibits [[RNA]] transcription enzymes, thereby blocking RNA synthesis and stopping the growth of cancerous cells.<ref name="Garrett1"/> Uracil can also be used in the synthesis of caffeine.<ref>{{cite journal|vauthors=Zajac MA, Zakrzewski AG, Kowal MG, Narayan S|date=2003|title=A novel method of caffeine synthesis from uracil|journal=Synthetic Communications|volume=33|issue=19|pages=3291–3297|doi=10.1081/SCC-120023986|s2cid=43220488}}</ref> Uracil has also shown potential as a HIV viral capsid inhibitor.<ref>{{cite journal | vauthors = Ramesh D, Mohanty AK, De A, Vijayakumar BG, Sethumadhavan A, Muthuvel SK, Mani M, Kannan T | display-authors = 6 | title = Uracil derivatives as HIV-1 capsid protein inhibitors: design, ''in silico'', ''in vitro'' and cytotoxicity studies | journal = RSC Advances | volume = 12 | issue = 27 | pages = 17466–17480 | date = June 2022 | pmid = 35765450 | pmc = 9190787 | doi = 10.1039/D2RA02450K | bibcode = 2022RSCAd..1217466R }}</ref> Uracil derivatives have antiviral, anti-tubercular and anti-leishmanial activity.<ref>{{Cite journal |last1=Ramesh |first1=Deepthi |last2=Vijayakumar |first2=Balaji Gowrivel |last3=Kannan |first3=Tharanikkarasu |date=2021-05-06 |title=Advances in Nucleoside and Nucleotide Analogues in Tackling Human Immunodeficiency Virus and Hepatitis Virus Infections |url=https://onlinelibrary.wiley.com/doi/10.1002/cmdc.202000849 |journal=ChemMedChem |language=en |volume=16 |issue=9 |pages=1403–1419 |doi=10.1002/cmdc.202000849 |pmid=33427377 |s2cid=231576801 |issn=1860-7179}}</ref><ref>{{Cite journal |last1=Ramesh |first1=Deepthi |last2=Vijayakumar |first2=Balaji Gowrivel |last3=Kannan |first3=Tharanikkarasu |date=2020-12-01 |title=Therapeutic potential of uracil and its derivatives in countering pathogenic and physiological disorders |url=https://www.sciencedirect.com/science/article/pii/S022352342030773X |journal=European Journal of Medicinal Chemistry |language=en |volume=207 |pages=112801 |doi=10.1016/j.ejmech.2020.112801 |pmid=32927231 |s2cid=221724578 |issn=0223-5234}}</ref><ref>{{cite journal | vauthors = Ramesh D, Sarkar D, Joji A, Singh M, Mohanty AK, G Vijayakumar B, Chatterjee M, Sriram D, Muthuvel SK, Kannan T | display-authors = 6 | title = First-in-class pyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones against leishmaniasis and tuberculosis: Rationale, in vitro, ex vivo studies and mechanistic insights | journal = Archiv der Pharmazie | volume = 355 | issue = 4 | pages = e2100440 | date = April 2022 | pmid = 35106845 | doi = 10.1002/ardp.202100440 | s2cid = 246474821 }}</ref>


Uracil can be used to determine [[microbial]] contamination of [[tomato]]es. The presence of uracil indicates [[lactic acid]] [[bacteria]] contamination of the fruit.<ref>{{cite journal | vauthors = Hidalgo A, Pompei C, Galli A, Cazzola S | title = Uracil as an index of lactic acid bacteria contamination of tomato products | journal = Journal of Agricultural and Food Chemistry | volume = 53 | issue = 2 | pages = 349–355 | date = January 2005 | pmid = 15656671 | doi = 10.1021/jf0486489 }}</ref> Uracil derivatives containing a [[diazine]] ring are used in [[pesticide]]s.<ref name = "Pozharskii1"/> Uracil derivatives are more often used as [[antiphotosynthesis|antiphotosynthetic]] [[herbicide]]s, destroying weeds in [[cotton]], [[sugar beet]], [[turnip]]s, [[soybean|soya]], [[pea]]s, [[sunflower]] crops, [[vineyard]]s, [[berry]] plantations, and [[orchard]]s.<ref name="Pozharskii1">{{cite book|title=Heterocycles in Life and Society: An introduction to heterocyclic chemistry and biochemistry and the role of heterocycles in science, technology, medicine, and agriculture|vauthors=Pozharskii AF, Soldatenkov AT, Katritzky AR|publisher=John Wiley and Sons|year=1997|isbn=9780471960348|location=New York, NY}}</ref>
Uracil can be used to determine [[microbial]] contamination of [[tomato]]es. The presence of uracil indicates [[lactic acid]] [[bacteria]] contamination of the fruit.<ref>{{cite journal | vauthors = Hidalgo A, Pompei C, Galli A, Cazzola S | title = Uracil as an index of lactic acid bacteria contamination of tomato products | journal = Journal of Agricultural and Food Chemistry | volume = 53 | issue = 2 | pages = 349–355 | date = January 2005 | pmid = 15656671 | doi = 10.1021/jf0486489 | bibcode = 2005JAFC...53..349H }}</ref> Uracil derivatives containing a [[diazine]] ring are used in [[pesticide]]s.<ref name = "Pozharskii1"/> Uracil derivatives are more often used as [[antiphotosynthesis|antiphotosynthetic]] [[herbicide]]s, destroying weeds in [[cotton]], [[sugar beet]], [[turnip]]s, [[soybean|soya]], [[pea]]s, [[sunflower]] crops, [[vineyard]]s, [[berry]] plantations, and [[orchard]]s.<ref name="Pozharskii1">{{cite book|title=Heterocycles in Life and Society: An introduction to heterocyclic chemistry and biochemistry and the role of heterocycles in science, technology, medicine, and agriculture|vauthors=Pozharskii AF, Soldatenkov AT, Katritzky AR|publisher=John Wiley and Sons|year=1997|isbn=9780471960348|location=New York, NY}}</ref> Uracil derivatives can enhance the activity of antimicrobial [[Polysaccharide|polysaccharides]] such as [[chitosan]].<ref>{{Cite journal |last1=Vijayakumar |first1=Balaji Gowrivel |last2=Ramesh |first2=Deepthi |last3=Manikandan |first3=K. Santhosh |last4=Theresa |first4=Mary |last5=Sethumadhavan |first5=Aiswarya |last6=Priyadarisini |first6=V. Brindha |last7=Radhakrishnan |first7=E. K. |last8=Mani |first8=Maheswaran |last9=Kannan |first9=Tharanikkarasu |date=2022-06-01 |title=Chitosan with pendant (E)-5-((4-acetylphenyl)diazenyl)-6-aminouracil groups as synergetic antimicrobial agents |url=https://pubs.rsc.org/en/content/articlelanding/2022/tb/d2tb00240j |journal=Journal of Materials Chemistry B |language=en |volume=10 |issue=21 |pages=4048–4058 |doi=10.1039/D2TB00240J |pmid=35507973 |s2cid=248526212 |issn=2050-7518}}</ref>


In [[yeast]], uracil concentrations are inversely proportional to uracil permease.<ref>{{cite journal | vauthors = Séron K, Blondel MO, Haguenauer-Tsapis R, Volland C | title = Uracil-induced down-regulation of the yeast uracil permease | journal = Journal of Bacteriology | volume = 181 | issue = 6 | pages = 1793–1800 | date = March 1999 | pmid = 10074071 | pmc = 93577 | doi = 10.1128/JB.181.6.1793-1800.1999 }}</ref>
In [[yeast]], uracil concentrations are inversely proportional to uracil permease.<ref>{{cite journal | vauthors = Séron K, Blondel MO, Haguenauer-Tsapis R, Volland C | title = Uracil-induced down-regulation of the yeast uracil permease | journal = Journal of Bacteriology | volume = 181 | issue = 6 | pages = 1793–1800 | date = March 1999 | pmid = 10074071 | pmc = 93577 | doi = 10.1128/JB.181.6.1793-1800.1999 }}</ref>

Latest revision as of 03:46, 11 December 2024

Uracil
Structural formula of uracil
Ball-and-stick model of uracil
Ball-and-stick model of uracil
Space-filling model of uracil
Space-filling model of uracil
Names
Preferred IUPAC name
Pyrimidine-2,4(1H,3H)-dione
Other names
  • 2-Oxy-4-oxypyrimidine
  • 2,4(1H,3H)-Pyrimidinedione
  • 2,4-Dihydroxypyrimidine
  • 2,4-Pyrimidinediol
Identifiers
3D model (JSmol)
3DMet
606623
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.565 Edit this at Wikidata
EC Number
  • 200-621-9
2896
KEGG
RTECS number
  • YQ8650000
UNII
  • InChI=1S/C4H4N2O2/c7-3-1-2-5-4(8)6-3/h1-2H,(H2,5,6,7,8) ☒N
    Key: ISAKRJDGNUQOIC-UHFFFAOYSA-N ☒N
Properties
C4H4N2O2
Molar mass 112.08676 g/mol
Appearance Solid
Density 1.32 g/cm3
Melting point 335 °C (635 °F; 608 K)[1]
Boiling point N/A – decomposes
Soluble
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
carcinogen and teratogen with chronic exposure
GHS labelling:
GHS07: Exclamation markGHS08: Health hazard
Warning
H315, H319, H335, H361
P201, P202, P261, P264, P271, P280, P281, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability (yellow): no hazard codeSpecial hazards (white): no code
1
1
Flash point Non-flammable
Related compounds
Related compounds
Thymine
Cytosine
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Uracil (/ˈjʊərəsɪl/) (symbol U or Ura) is one of the four nucleotide bases in the nucleic acid RNA. The others are adenine (A), cytosine (C), and guanine (G). In RNA, uracil binds to adenine via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine (T). Uracil is a demethylated form of thymine.

Uracil is a common and naturally occurring pyrimidine derivative.[2] The name "uracil" was coined in 1885 by the German chemist Robert Behrend, who was attempting to synthesize derivatives of uric acid.[3] Originally discovered in 1900 by Alberto Ascoli, it was isolated by hydrolysis of yeast nuclein;[4] it was also found in bovine thymus and spleen, herring sperm, and wheat germ.[5] It is a planar, unsaturated compound that has the ability to absorb light.[6]

Uracil that was formed extraterrestrially has been detected in the Murchison meteorite,[7] in near-Earth asteroid Ryugu,[8] and possibly on the surface of the moon Titan.[9] It has been synthesized under cold laboratory conditions similar to outer space, from pyrimidine embedded in water ice and exposed to ultraviolet light.[10]

Properties

[edit]

In RNA, uracil base-pairs with adenine and replaces thymine during DNA transcription. Methylation of uracil produces thymine.[11] In DNA, the evolutionary substitution of thymine for uracil may have increased DNA stability and improved the efficiency of DNA replication (discussed below). Uracil pairs with adenine through hydrogen bonding. When base pairing with adenine, uracil acts as both a hydrogen bond acceptor and a hydrogen bond donor. In RNA, uracil binds with a ribose sugar to form the ribonucleoside uridine. When a phosphate attaches to uridine, uridine 5′-monophosphate is produced.[6]

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.[5] 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 tautomers: Amide or lactam structure (left) and imide or lactim structure (right)

Uracil also recycles itself to form nucleotides by undergoing a series of phosphoribosyltransferase reactions.[2] Degradation of uracil produces the substrates β-alanine, carbon dioxide, and ammonia.[2]

C4H4N2O2H3NCH2CH2COO + NH+4 + CO2

Oxidative degradation of uracil produces urea and maleic acid in the presence of H2O2 and Fe2+ or in the presence of diatomic oxygen and Fe2+.

Uracil is a weak acid. The first site of ionization of uracil is not known.[12] The negative charge is placed on the oxygen anion and produces a pKa of less than or equal to 12. The basic pKa = −3.4, while the acidic pKa = 9.389. In the gas phase, uracil has four sites that are more acidic than water.[13]

In DNA

[edit]

Uracil is rarely found in DNA, and this may have been an evolutionary change to increase genetic stability. This is because cytosine can deaminate spontaneously to produce uracil through hydrolytic deamination. Therefore, if there were an organism that used uracil in its DNA, the deamination of cytosine (which undergoes base pairing with guanine) would lead to formation of uracil (which would base pair with adenine) during DNA synthesis. Uracil-DNA glycosylase excises uracil bases from double-stranded DNA. This enzyme would therefore recognize and cut out both types of uracil – the one incorporated naturally, and the one formed due to cytosine deamination, which would trigger unnecessary and inappropriate repair processes.[14]

This problem is believed to have been solved in terms of evolution, that is by "tagging" (methylating) uracil. Methylated uracil is identical to thymine. Hence the hypothesis that, over time, thymine became standard in DNA instead of uracil. So cells continue to use uracil in RNA, and not in DNA, because RNA is shorter-lived than DNA, and any potential uracil-related errors do not lead to lasting damage. Apparently, either there was no evolutionary pressure to replace uracil in RNA with the more complex thymine, or uracil has some chemical property that is useful in RNA, which thymine lacks. Uracil-containing DNA still exists, for example in:

Synthesis

[edit]

Biological

[edit]

Organisms synthesize uracil, in the form of uridine monophosphate (UMP), by decarboxylating orotidine 5'-monophosphate (orotidylic acid). In humans this decarboxylation is achieved by the enzyme UMP synthase. In contrast to the purine nucleotides, the pyrimidine ring (orotidylic acid) that leads uracil is synthesized first and then linked to ribose phosphate, forming UMP.[16]

Laboratory

[edit]

There are many laboratory synthesis of uracil available. The first reaction is the simplest of the syntheses, by adding water to cytosine to produce uracil and ammonia:[2]

C4H5N3O + H2OC4H4N2O2 + NH3

The most common way to synthesize uracil is by the condensation of malic acid with urea in fuming sulfuric acid:[5]

C4H4O4 + NH2CONH2C4H4N2O2 + 2 H2O + CO

Uracil can also be synthesized by a double decomposition of thiouracil in aqueous chloroacetic acid.[5]

Photodehydrogenation of 5,6-diuracil, which is synthesized by beta-alanine reacting with urea, produces uracil.[17]

Prebiotic

[edit]

In 2009, NASA scientists reported having produced uracil from pyrimidine and water ice by exposing it to ultraviolet light under space-like conditions.[10] This suggests a possible natural original source for uracil.[18] In 2014, NASA scientists reported that additional complex DNA and RNA organic compounds of life, including uracil, cytosine and thymine, have been formed in the laboratory under outer space conditions, starting with ice, pyrimidine, ammonia, and methanol, which are compounds found in astrophysical environments.[19] Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), a carbon-rich chemical found in the Universe, may have been formed in red giants or in interstellar dust and gas clouds.[20]

Based on 12C/13C isotopic ratios of organic compounds found in the Murchison meteorite, it is believed that uracil, xanthine, and related molecules can also be formed extraterrestrially.[7] Data from the Cassini mission, orbiting in the Saturn system, suggests that uracil is present in the surface of the moon Titan.[9] In 2023, uracil was observed in a sample from 162173 Ryugu, a near-Earth asteroid, with no exposure to Earth's biosphere, giving further evidence for synthesis in space.[8]

Reactions

[edit]
Chemical structure of uridine

Uracil readily undergoes regular reactions including oxidation, nitration, and alkylation. While in the presence of phenol (PhOH) and sodium hypochlorite (NaOCl), uracil can be visualized in ultraviolet light.[5] Uracil also has the capability to react with elemental halogens because of the presence of more than one strongly electron donating group.[5]

Uracil readily undergoes addition to ribose sugars and phosphates to partake in synthesis and further reactions in the body. Uracil becomes uridine, uridine monophosphate (UMP), uridine diphosphate (UDP), uridine triphosphate (UTP), and uridine diphosphate glucose (UDP-glucose). Each one of these molecules is synthesized in the body and has specific functions.

When uracil reacts with anhydrous hydrazine, a first-order kinetic reaction occurs and the uracil ring opens up.[21] If the pH of the reaction increases to > 10.5, the uracil anion forms, making the reaction go much more slowly. The same slowing of the reaction occurs if the pH decreases, because of the protonation of the hydrazine.[21] The reactivity of uracil remains unchanged, even if the temperature changes.[21]

Uses

[edit]

Uracil's use in the body is to help carry out the synthesis of many enzymes necessary for cell function through bonding with riboses and phosphates.[2] Uracil serves as allosteric regulator and coenzyme for reactions in animals and in plants.[22] UMP controls the activity of carbamoyl phosphate synthetase and aspartate transcarbamoylase in plants, while UDP and UTP regulate CPSase II activity in animals. UDP-glucose regulates the conversion of glucose to galactose in the liver and other tissues in the process of carbohydrate metabolism.[22] Uracil is also involved in the biosynthesis of polysaccharides and the transportation of sugars containing aldehydes.[22] Uracil is important for the detoxification of many carcinogens, for instance those found in tobacco smoke.[23] Uracil is also required to detoxify many drugs such as cannabinoids (THC)[24] and morphine (opioids).[25] It can also slightly increase the risk for cancer in unusual cases in which the body is extremely deficient in folate.[26] The deficiency in folate leads to increased ratio of deoxyuridine monophosphates (dUMP)/deoxythymidine monophosphates (dTMP) and uracil misincorporation into DNA and eventually low production of DNA.[26]

Uracil can be used for drug delivery and as a pharmaceutical. When elemental fluorine reacts with uracil, they produce 5-fluorouracil. 5-Fluorouracil is an anticancer drug (antimetabolite) used to masquerade as uracil during the nucleic acid replication process.[2] Because 5-fluorouracil is similar in shape to, but does not undergo the same chemistry as, uracil, the drug inhibits RNA transcription enzymes, thereby blocking RNA synthesis and stopping the growth of cancerous cells.[2] Uracil can also be used in the synthesis of caffeine.[27] Uracil has also shown potential as a HIV viral capsid inhibitor.[28] Uracil derivatives have antiviral, anti-tubercular and anti-leishmanial activity.[29][30][31]

Uracil can be used to determine microbial contamination of tomatoes. The presence of uracil indicates lactic acid bacteria contamination of the fruit.[32] Uracil derivatives containing a diazine ring are used in pesticides.[33] Uracil derivatives are more often used as antiphotosynthetic herbicides, destroying weeds in cotton, sugar beet, turnips, soya, peas, sunflower crops, vineyards, berry plantations, and orchards.[33] Uracil derivatives can enhance the activity of antimicrobial polysaccharides such as chitosan.[34]

In yeast, uracil concentrations are inversely proportional to uracil permease.[35]

Mixtures containing uracil are also commonly used to test reversed-phase HPLC columns. As uracil is essentially unretained by the non-polar stationary phase, this can be used to determine the dwell time (and subsequently dwell volume, given a known flow rate) of the system.

References

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