Goldman G H, Yu C, Wu H Y, Sanders M M, La Voie E J, Liu L F
Faculdade de Ciências Farmaceuticas de Ribeirão Preto, Universidade de São Paulo, Brazil.
Biochemistry. 1997 May 27;36(21):6488-94. doi: 10.1021/bi963033t.
DNA topoisomerase I has been partially purified from Aspergillus nidulans. The purified enzyme is most likely the major nuclear DNA topoisomerase I on the basis of the following findings. (1) Purified DNA topoisomerase I can relax both positively and negatively supercoiled DNA. (2) Neither an energy cofactor nor Mg(II) is required for the relaxation or the cleavage reaction of the enzyme. On the basis of a phosphate-transfer experiment, the Aspergillus topoisomerase I was shown to have a molecular mass (Mr) of 105 kDa. The differential sensitivity of the human and Aspergillus topoisomerase I was compared using a number of known human DNA topoisomerase I poisons. Like human DNA topoisomerase I, Aspergillus topoisomerase I is highly sensitive to the poisoning activity of camptothecin and a number of bi- and terbenzimidazoles. However, unlike human topoisomerase I, Aspergillus topoisomerase I is completely resistant to monobenzimidazoles, protoberberines (e.g. coralyne), and nitidine. Cytotoxicity studies using yeast expressing human and yeast topoisomerase I cDNAs have also demonstrated a similar differential sensitivity of yeast topoisomerase I to these human topoisomerase I poisons. These results together suggest that the nuclear fungal topoisomerase I may be sufficiently different from its human counterpart to serve as a molecular target for the development of antifungal drugs.
已从构巢曲霉中部分纯化出DNA拓扑异构酶I。基于以下发现，纯化后的酶很可能是主要的核DNA拓扑异构酶I。（1）纯化的DNA拓扑异构酶I可以使正超螺旋和负超螺旋DNA松弛。（2）该酶的松弛或切割反应既不需要能量辅助因子也不需要Mg（II）。基于磷酸转移实验，构巢曲霉拓扑异构酶I的分子量（Mr）为105 kDa。使用多种已知的人DNA拓扑异构酶I抑制剂比较了人和构巢曲霉拓扑异构酶I的差异敏感性。与人类DNA拓扑异构酶I一样，构巢曲霉拓扑异构酶I对喜树碱以及多种双苯并咪唑和三苯并咪唑的抑制活性高度敏感。然而，与人类拓扑异构酶I不同，构巢曲霉拓扑异构酶I对单苯并咪唑、原小檗碱（如珊瑚碱）和两面针碱完全耐药。使用表达人及酵母拓扑异构酶I cDNA的酵母进行的细胞毒性研究也证明了酵母拓扑异构酶I对这些人DNA拓扑异构酶I抑制剂具有类似的差异敏感性。这些结果共同表明，核真菌拓扑异构酶I与其人类对应物可能存在足够差异，可作为开发抗真菌药物的分子靶点。
