Key decatenating enzyme that alters DNA topology by binding to two double-stranded DNA molecules, generating a double-stranded break in one of the strands, passing the intact strand through the broken strand, and religating the broken strand. Plays a role in B-cell differentiation. ATP-dependent breakage, passage and rejoining of double-stranded DNA. Binds two Mg(2+) per subunit. The magnesium ions form salt bridges with both the protein and the DNA. Can also accept other divalent metal cations, such as Mn(2+) or Ca(2+). Homodimer (PubMed:21778401). Interacts with KIAA1210 (By similarity). Interacts with PLSCR1 (PubMed:19690332). Expressed in the tonsil, spleen, lymph node, thymus, skin, pancreas, testis, colon, kidney, liver, brain and lung (PubMed:9155056). Also found in breast, colon and lung carcinomas, Hodgkin's disease, large-cell non-Hodgkin's lymphoma, lymphocytic lymphomas and seminomas (PubMed:9155056). Defects in TOP2B may be involved in global developmental delay with autism spectrum disorder (ASD). The disease is caused by variants affecting the gene represented in this entry. Eukaryotic topoisomerase I and II can relax both negative and positive supercoils, whereas prokaryotic enzymes relax only negative supercoils. Belongs to the type II topoisomerase family.