DNA topoisomerase

DNA topoisomerase (EC 5.99.1.2, type I DNA topoisomerase, untwisting enzyme, relaxing enzyme, nicking-closing enzyme, swivelase, omega-protein, deoxyribonucleate topoisomerase) is an enzyme with systematic name DNA topoisomerase. This enzyme catalyses the following chemical reaction

ATP-independent breakage of single-stranded DNA, followed by passage and rejoining

These enzymes bring about the conversion of one topological isomer of DNA into another. There are two types of DNA topoisomerase; I and II. Both of which are further classified into sub families IA, IB, IIA, and IIB. DNA topoisomerase facilitates a transesterification reaction. Through this reaction DNA topoisomerase is able to break and rejoin the phosphate backbone of DNA.