Based on homology with E. coli AlkB, nine mammalian AlkB homologues have been identified. Like E. coli AlkB, ALKBH2 and ALKBH3 have been shown to possess DNA repair activity. However, findings suggest a wide functional diversity for other mammalian AlkB proteins, with substrates ranging from DNA and RNA to protein [, ].AlkB homologue 6 (ALKBH6) is a probable dioxygenase that requires molecular oxygen, alpha-ketoglutarate and iron. Its function is not known.