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Deamination is the removal of an amino group from a molecule. [1] Enzymes that catalyse this reaction are called deaminases. In the human body, deamination takes place primarily in the liver; however, it can also occur in the kidney. In situations of excess protein intake, deamination is used to break down amino acids for energy.
Cytosine can also be methylated into 5-methylcytosine by an enzyme called DNA methyltransferase or be methylated and hydroxylated to make 5-hydroxymethylcytosine. The difference in rates of deamination of cytosine and 5-methylcytosine (to uracil and thymine ) forms the basis of bisulfite sequencing .
This underrepresentation is a consequence of the high mutation rate of methylated CpG sites: the spontaneously occurring deamination of a methylated cytosine results in a thymine, and the resulting G:T mismatched bases are often improperly resolved to A:T; whereas the deamination of unmethylated cytosine results in a uracil, which as a foreign ...
Activation-induced cytidine deaminase, also known as AICDA, AID and single-stranded DNA cytosine deaminase, is a 24 kDa enzyme which in humans is encoded by the AICDA gene. [5] It creates mutations in DNA [6] [7] by deamination of cytosine base, which turns it into uracil (which is recognized as a thymine). In other words, it changes a C:G base ...
Cytosine deamination commonly occurs under physiological conditions and essentially is the deamination of cytosine. This process yields uracil as its product, which is not a base pair found within DNA. This process causes extensive DNA damage.
In enzymology, a cytosine deaminase (EC 3.5.4.1) is an enzyme that catalyzes the chemical reaction cytosine + H 2 O ⇌ {\displaystyle \rightleftharpoons } uracil + NH 3 Thus, the two substrates of this enzyme are cytosine [ 1 ] and H 2 O , whereas its two products are uracil and NH 3 .
5-Methylcytosine (5mC) is a methylated form of the DNA base cytosine (C) that regulates gene transcription and takes several other biological roles. [1] When cytosine is methylated, the DNA maintains the same sequence, but the expression of methylated genes can be altered (the study of this is part of the field of epigenetics). 5-Methylcytosine is incorporated in the nucleoside 5-methylcytidine.
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.