Relaxes both positive and negative superturns and exhibits a strong decatenase activity. ATP-dependent breakage, passage and rejoining of double-stranded DNA. Mg(2+) is directly coordinated by Glu-197 and Asp-249 as well as indirectly coordinated through 2 water molecules by Asp-251 (PubMed:10545127). Homodimer (PubMed:10545127). Heterotetramer of two Top6A and two Top6B chains. Belongs to the TOP6A family.