AlkB is an E.coli alpha-ketoglutarate- and Fe(II)-dependent dioxygenase that oxidizes the relevant methyl groups and releases them as formaldehyde. Two human homologs of AlkB, ALKBH2 and ALKBH3, both remove 1-methyladenine (1-meA) and 3-methylcytosine (3-meC) from methylated polynucleotides in an alpha-ketoglutarate-dependent reaction. They act by direct damage reversal with the regeneration of the unsubstituted bases. E.coli AlkB and human ALKBH2 and ALKBH3 can also repair 1-ethyladenine (1-etA) residues in DNA with the release of acetaldehyde (Duncan et al., 2002, Lee et al. 2005).