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. Author manuscript; available in PMC: 2014 Jul 1.
Published in final edited form as: Mol Aspects Med. 2012 Jul 10;34(4):813–825. doi: 10.1016/j.mam.2012.06.008

Figure 6. Deamination of cytosine by AID.

Figure 6

The proposed mechanism for enzymatic deamination of cytosine by AID/APOBEC enzymes involves production of an activated intermediate where the enzyme is covalently linked to the pyrimidine base through an oxygen atom. The intermediate is resolved by attack of a water molecule, regenerating the active enzyme and uracil. The reaction mechanism proceeds unaltered in the presence of a methyl carbon at the 5 position of the ring. However, the resulting product is thymidine, rather than uracil.