IUBMB Enzyme Nomenclature


Accepted name: DNA topoisomerase

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

Other name(s): type I DNA topoisomerase; untwisting enzyme; relaxing enzyme; nicking-closing enzyme; swivelase; ω-protein; deoxyribonucleate topoisomerase; topoisomerase

Systematic name: DNA topoisomerase

Comments: These enzymes bring about the conversion of one topological isomer of DNA into another, e.g., the relaxation of superhelical turns in DNA, the interconversion of simple and knotted rings of single-stranded DNA, and the intertwisting of single-stranded rings of complementary sequences, cf. EC DNA topoisomerase (ATP-hydrolysing).

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Gellert, M. DNA topoisomerases. Annu. Rev. Biochem. 50 (1981) 879-910. [PMID: 6267993]

[EC created 1984 as transferred 2018 to EC]

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