Compounds that inhibit the enzymatic activity of topoisomerases. Topoisomerases I and II are involved in the interconversion of DNA forms differing in their linking number "L". Topoisomerase I acts by introducing transient nicks in the DNA, while topoisomerase II acts via intermediates containing double-stranded DNA cuts and requires ATP for its action. The change in linking number (delta L) serves to measure the topological changes occurring in DNA during structural transformations (e.g. palindrome extrusion, Z-DNA formation, transcription factor binding, transcription).
