WordNet

remove the amino radical (usually by hydrolysis) from an amino compound; to perform deamination (同)deaminize
removal of the amino radical from an amino acid or other amino compound (同)deaminization

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/03/07 12:57:26」(JST)

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Deamination is the removal of an amine 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. Deamination is the process by which amino acids are broken down if there is an excess of protein intake. 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.

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 converts 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 can be corrected by the enzyme thymine-DNA glycosylase prior to passage of the replication fork, which would fix the cytosine to thymine point mutation in one of the two daughter strands.^[1]

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 (AID)
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)

References

^ 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.

English Journal

Potent and Selective Inhibition of A-to-I RNA Editing with 2'-O-Methyl/Locked Nucleic Acid-containing Antisense Oligoribonucleotides.

Mizrahi RA, Schirle NT, Beal PA.AbstractADARs (adenosine deaminases acting on RNA) are RNA editing enzymes that bind double helical RNAs and deaminate select adenosines (A). The product inosine (I) is read during translation as guanosine (G) so such changes can alter codon meaning. ADAR-catalyzed A to I changes occur in coding sequences for several proteins of importance to the nervous system. However, these sites constitute only a very small fraction of known A to I sites in the human transcriptome and the significance of editing at the vast majority sites is unknown at this time. Site-selective inhibitors of RNA editing are needed to advance our understanding of the function of editing at specific sites. Here we show that 2'-O-methyl/locked nucleic acid (LNA) mixmer antisense oligonucleotides are potent and selective inhibitors of RNA editing on two different target RNAs. These reagents are capable of binding with high affinity to RNA editing substrates and remodeling the secondary structure by a strand-invasion mechanism. The potency observed here for 2'-O-methyl/LNA mixmers suggests this backbone structure is superior to the morpholino backbone structure for inhibition of RNA editing. Finally, we demonstrate antisense inhibition of editing of the mRNA for the DNA repair glycosylase NEIL1 in cultured human cells providing a new approach to exploring the link between RNA editing and the cellular response to oxidative DNA damage.
ACS chemical biology.ACS Chem Biol.2013 Feb 11. [Epub ahead of print]
ADARs (adenosine deaminases acting on RNA) are RNA editing enzymes that bind double helical RNAs and deaminate select adenosines (A). The product inosine (I) is read during translation as guanosine (G) so such changes can alter codon meaning. ADAR-catalyzed A to I changes occur in coding sequences
PMID 23394403

RNA editing of hepatitis B virus transcripts by activation-induced cytidine deaminase.

Liang G, Kitamura K, Wang Z, Liu G, Chowdhury S, Fu W, Koura M, Wakae K, Honjo T, Muramatsu M.SourceDepartment of Immunology and Genomic Medicine, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
Proceedings of the National Academy of Sciences of the United States of America.Proc Natl Acad Sci U S A.2013 Feb 5;110(6):2246-51. doi: 10.1073/pnas.1221921110. Epub 2013 Jan 22.
Activation-induced cytidine deaminase (AID) is essential for the somatic hypermutation (SHM) and class-switch recombination (CSR) of Ig genes. The mechanism by which AID triggers SHM and CSR has been explained by two distinct models. In the DNA deamination model, AID converts cytidine bases in DNA i
PMID 23341589

HIV-1 Vif alters processive single-stranded DNA scanning of the retroviral restriction factor APOBEC3G.

Feng Y, Love RP, Chelico L.SourceUniversity of Saskatchewan, Canada.
The Journal of biological chemistry.J Biol Chem.2013 Jan 11. [Epub ahead of print]
APOBEC3G is a retroviral restriction factor that can inhibit the replication of HIV-1 in the absence of the viral infectivity factor (Vif) protein. Virion encapsidated APOBEC3G can deaminate cytosine to uracil in viral (-)DNA which leads to hypermutation and inactivation of the provirus. APOBEC3G ca
PMID 23316055