DNA topoisomerase 3-beta-1 (TOP3B)

Releases the supercoiling and torsional tension of DNA introduced through the DNA replication and transcription by transiently cleaving and rejoining one strand of the DNA duplex. Introduces a single-strand break through transesterification at a target site in duplex DNA.

The scissile phosphodiester is attacked by the catalytic tyrosine of this enzyme, resulting in the formation of a DNA-(5'-phosphotyrosyl)-enzyme intermediate and the expulsion of a 3'-OH DNA strand. The free DNA strand than undergoes passage around the unbroken strand thus removing DNA supercoils.