Histone demethylase that specifically demethylates 'Lys-9' of histone H3, thereby playing a role in histone code. Does not demethylate histone H3 'Lys-4', H3 'Lys-27', H3 'Lys-36' nor H4 'Lys-20'. Only able to demethylate trimethylated H3 'Lys-9', with a weaker activity than KDM4A, KDM4C and KDM4D. Demethylation of Lys residue generates formaldehyde and succinate.,JMJD2B, TDRD14B,Cell Biology & Developmental Biology,Cell Cycle,DNA Damage & Repair,Epigenetic writers and erasers of core Histones,Epigenetic writers and erasers of core Histones_Demethylation,Epigenetics & Nuclear Signaling,Immunology & Inflammation,Kinase,Kinase_Serine/threonine kinases,Nuclear Receptor Signaling,Signal Transduction,KDM4B