Douc-Rasy S, Kayser A, Riou J F, Riou G
Proc Natl Acad Sci U S A. 1986 Oct;83(19):7152-6. doi: 10.1073/pnas.83.19.7152.
We have characterized in Trypanosoma cruzi a DNA topoisomerase capable of decatenating complex trypanosomal kinetoplast DNA networks in the absence of ATP. The enzymatic activity requires Mg2+ and K+. Using a defined DNA topoisomer we showed that the linking number changes by steps of 2, which characterizes the enzyme as a type II topoisomerase. The enzyme can catenate supercoiled DNA molecules, unknot DNA, and cleave double-stranded DNA. The enzyme has no ATPase activity. The native enzyme has an Mr of about 200,000. Crude extracts and partially purified fractions contain an aggregating factor that can substitute spermidine in catenating reactions. Because of the presence of this factor, the kinetoplast DNA can only be decatenated by purified fractions. The enzyme is inhibited by certain drugs and provides a potential target for chemotherapy. Such an enzyme was also characterized in Trypanosoma equiperdum.
我们已经在克氏锥虫中鉴定出一种DNA拓扑异构酶，该酶在没有ATP的情况下能够解开复杂的锥虫动基体DNA网络。这种酶活性需要Mg2+和K+。使用一种确定的DNA拓扑异构体，我们发现连接数以2的步长变化，这表明该酶是一种II型拓扑异构酶。该酶能够连接超螺旋DNA分子、解开DNA结并切割双链DNA。该酶没有ATP酶活性。天然酶的分子量约为200,000。粗提物和部分纯化的组分中含有一种聚集因子，该因子在连接反应中可以替代亚精胺。由于这种因子的存在，动基体DNA只能被纯化的组分解开。该酶受到某些药物的抑制，为化疗提供了一个潜在靶点。在马媾疫锥虫中也鉴定出了这样一种酶。
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