Recombinant JMJD1B / KDM3B (accession number NP_057688.2) was expressed in Sf9 cells and contains an N-terminal FLAG tag with a molecular weight of 193.4 kDa. Lysine (K)-specific demethylase 3B (KDM3B), also known as Jumonji domain-containing protein 1B (JMJD1B), is a histone demethylase that specifically demethylates lysine 9 of histone H3 (H3K9), thereby playing a central role in defining the histone code. Demethylation of lysine residues generates formaldehyde and succinate. KDM3B may have tumor suppressor activity.