ATP-independent type II topoisomerase from trypanosomes.

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.