biological role topoisomerase I inhibitor topoisomerase I inhibitors EC 5.99.1.2 inhibitor chebi_ontology type I DNA topoisomerase inhibitor type I DNA topoisomerase inhibitors CHEBI:50276 A topoisomerase inhibitor that inhibits the bacterial enzymes of the DNA topoisomerases, Type I class (EC5.99.1.2) that catalyze ATP-independent breakage of one of the two strands of DNA, passage of the unbroken strand through the break, and rejoining of the broken strand. These bacterial enzymes reduce the topological stress in the DNA structure by relaxing negatively, but not positively, supercoiled DNA. EC 5.99.1.2 inhibitors topoisomerase inhibitor DNA topoisomerase type I activity