Deamination - wikipedia Deamination This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( March 2014 ) Deamination is the removal of an amino group from a molecule. Enzymes that catalyse this reaction are called deaminases. In the human body, deamination takes place primarily in the liver, however glutamate is also deaminated in the kidneys. In situations of excess protein intake, deamination is used to break down amino acids for energy. The amino group is removed from the amino acid and converted to ammonia. The rest of the amino acid is made up of mostly carbon and hydrogen, and is recycled or oxidized for energy. Ammonia is toxic to the human system, and enzymes convert it to urea or uric acid by addition of carbon dioxide molecules ( which is not considered a deamination process ) in the urea cycle, which also takes place in the liver. Urea and uric acid can safely diffuse into the blood and then be excreted in urine. Contents 1 Deamination reactions in DNA 1.1 Cytosine 1.2 5 - methylcytosine 1.3 Guanine 1.4 Adenine 2 Additional proteins performing this function 3 See also 4 References Deamination reactions in DNA Cytosine Spontaneous deamination is the hydrolysis reaction of cytosine into uracil, releasing ammonia in the process. This can occur in vitro through the use of bisulfite, which deaminates cytosine, but not 5 - methylcytosine. This property has allowed researchers to sequence methylated DNA to distinguish non-methylated cytosine ( shown up as uracil ) and methylated cytosine ( unaltered ). In DNA, this spontaneous deamination is corrected for by the removal of uracil ( product of cytosine deamination and not part of DNA ) by uracil - DNA glycosylase, generating an abasic ( AP ) site. The resulting abasic site is then recognised by enzymes ( AP endonucleases ) that break a phosphodiester bond in the DNA, permitting the repair of the resulting lesion by replacement with another cytosine. A DNA polymerase may perform this replacement via nick translation, a terminal excision reaction by its 5 ' -- > 3 ' exonuclease activity, followed by a fill - in reaction by its polymerase activity. DNA ligase then forms a phosphodiester bond to seal the resulting nicked duplex product, which now includes a new, correct cytosine. ( See Base excision repair. ) 5 - methylcytosine Spontaneous deamination of 5 - methylcytosine results in thymine and ammonia. This is the most common single nucleotide mutation. In DNA, this reaction, if detected prior to passage of the replication fork, can be corrected by the enzyme thymine - DNA glycosylase, which removes the thymine base in a G / T mismatch. This leaves an abasic site that is repaired by AP endonucleases and polymerase, like with uracil - DNA glycosylase. Guanine Deamination of guanine results in the formation of xanthine. Xanthine, in a manner analogous to the enol tautomer of guanine, selectively base pairs with thymine instead of cytosine. This results in a post-replicative transition mutation, where the original G-C base pair transforms into an A-T base pair. Correction of this mutation involves the use of alkyladenine glycosylase ( Aag ) during base excision repair. Adenine Deamination of adenine results in the formation of hypoxanthine. Hypoxanthine, in a manner analogous to the imine tautomer of adenine, selectively base pairs with cytosine instead of thymine. This results in a post-replicative transition mutation, where the original A-T base pair transforms into a G-C base pair. Additional proteins performing this function APOBEC1 APOBEC3A - H, APOBEC3G - affects HIV Activation - induced ( cytidine ) deaminase ( AICDA ) AMP deaminase ( AMPD1 ) Cytodine deaminase of mononucelotides ( CDA ) Adenosine Deaminase acting on tRNA ( ADAT ) Adenosine Deaminase acting on dsRNA ( ADAR ) Adenosine Deaminase acting on mononucleotides ( ADA ) Guanine Deaminase ( GDA ) See also Adenosine monophosphate deaminase deficiency type 1 References Jump up ^ Gallinari, P. ( 1996 ). `` Cloning and Expression of Human G / T Mismatch - specific Thymine - DNA Glycosylase ''. Journal of Biological Chemistry. 271 ( 22 ) : 12767 -- 74. doi : 10.1074 / jbc. 271.22. 12767. PMID 8662714. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Deamination&oldid=811544648 '' Categories : Metabolism Substitution reactions Hidden categories : Articles needing additional references from March 2014 All articles needing additional references Talk Contents About Wikipedia Bosanski Català Čeština Dansk Deutsch Ελληνικά Français Հայերեն हिन्दी Bahasa Indonesia Italiano עברית Nederlands 日本 語 Polski Русский Српски / srpski Srpskohrvatski / српскохрватски Svenska Türkçe Українська 中文 Edit links This page was last edited on 22 November 2017, at 08 : 57. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: where are unwanted amino acids converted into urea
Answer: liver