Dioxygenase that repairs alkylated DNA containing 1-methyladenine and 1-ethenoadenine by oxidative demethylation. Accepts double-stranded and single-stranded substrates, with a preference for dsDNA over ssDNA. Confers resistance to methylating agents such as methylmethanesulphonate (MMS). 2-oxoglutarate + a methylated nucleobase within DNA + O2 = a nucleobase within DNA + CO2 + formaldehyde + succinate Binds 1 Fe(2+) ion per subunit. Expressed ubiquitously, including in seedlings, leaves and flowers. In seedlings, mostly present in the shoot meristematic region, as well as in the vasculature of the hypocotyl and root. Expressed in both primary and lateral root vasculature. In flowers, accumulates in sepals, stem, carpel tissue and anther filaments. Enhanced sensitivity to the methylating agent methylmethanesulphonate (MMS) leading to abnormal seedlings in presence of MMS. Belongs to the alkB family.