Duguet M, Lavenot C, Harper F, Mirambeau G, De Recondo A M
Nucleic Acids Res. 1983 Feb 25;11(4):1059-75. doi: 10.1093/nar/11.4.1059.
Besides the nicking-closing (topoisomerase I) activity, an ATP-dependent DNA topoisomerase is present in rat liver nuclei. The enzyme, partially purified, is able to catenate in vitro closed DNA circles in a magnesium-dependent, ATP-dependent, histone H1-dependent reaction, and to decatenate in vitro kinetoplast DNA networks to yield free minicircles in a magnesium-dependent and ATP-dependent reaction. It is largely similar to other eukaryotic type II topoisomerases in its requirements, and presumably belongs to this class of enzymes. Type I and type II activities were measured in rat liver nuclei as a function of regenerating time after partial hepatectomy: type I activity was not significantly changed during this process. In contrast, type II activity was considerably increased, suggesting a possible involvement of the enzyme in DNA replication.
除了切口封闭（拓扑异构酶I）活性外，大鼠肝细胞核中还存在一种依赖ATP的DNA拓扑异构酶。部分纯化的这种酶能够在体外以依赖镁、依赖ATP、依赖组蛋白H1的反应将闭合的DNA环连接起来，并在体外以依赖镁和依赖ATP的反应解开动质体DNA网络，产生游离的微小环。在其需求方面，它与其他真核II型拓扑异构酶大体相似，推测属于这类酶。在大鼠肝细胞核中，I型和II型活性作为部分肝切除术后再生时间的函数进行了测定：在此过程中I型活性没有显著变化。相比之下，II型活性显著增加，表明该酶可能参与DNA复制。
