AlkB

AlkB protein is a protein induced during an adaptive response and is involved in the direct reversal of alkylation damage. AlkB specifically removes alkylation damage to single stranded (SS) DNA caused by S_N2 type of chemical agents. It efficiently removes methyl groups from 1-methyl adenines, 3-methyl cytosines in SS DNA. AlkB belongs to the Fe (II)/2-oxoglutarate-dependent dioxygenase superfamily and oxidatively demethylates the DNA substrate.Demethylation by AlkB is accompanied with release of CO₂, succinate and formaldehyde.

Human homologs

There are nine human homologs of AlkB. They are:

ABH3, like E. coli AlkB, is specific for SS DNA and RNA whereas ABH2 has higher affinity for damages in double-stranded DNA.

ALKBH8 has a RNA recognition motif, a methyltransferase domain, and an AlkB-like domain. The methyltransferase domain generates the wobble nucleoside 5-methoxycarbonylmethyluridine (mcm5U) from its precursor 5-carboxymethyluridine (cm5U). The AlkB-like domain generates (S)-5-methoxycarbonylhydroxymethyluridine (mchm5U)in Gly-tRNA-UCC.

DNA oxidative demethylase

DNA oxidative demethylase (EC 1.14.11.33, alkylated DNA repair protein, alpha-ketoglutarate-dependent dioxygenase ABH1, alkB (gene)) is an enzyme with system name methyl DNA-base, 2-oxoglutarate:oxygen oxidoreductase (formaldehyde-forming). This enzyme catalyses the following chemical reaction

DNA oxidative demethylase contains iron; activity is somewhat stimulated by ascorbate.

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