The Great Oxygenation Event, which occurred on earth around 2.45 billion years ago, opened up the niche for enzymes that could directly oxidize substrates using molecular oxygen (O2), including the 2-oxoglutarate (2OG) and Fe(II)-dependent dioxygenases. 2OGFe-dioxygenases possess a double-stranded β-helix, with an iron center chelated by two histidines and an aspartate.(1) 2OGFe-dioxygenases catalyze the incorporation of one atom of O2 into 2-oxoglutarate, oxidizing it to succinate, and the second atom into an organic substrate. The AlkB family and related clades catalyze this reaction on alkyl adducts on nitrogens of bases, whereas the TET/JBP family catalyzes the oxidation of methyl groups attached to carbons of bases.(1) As enzymes that generate epigenetic marks by modifying DNA or RNA, members of both the AlkB and TET/JBP families have been repeatedly recruited to different eukaryotic lineages.