Castelli Silvia, Campagna Alessia, Vassallo Oscar, Tesauro Cinzia, Fiorani Paola, Tagliatesta Pietro, Oteri Francesco, Falconi Mattia, Majumder Hemanta K, Desideri Alessandro
Department of Biology, University of Rome Tor Vergata, Italy.
Arch Biochem Biophys. 2009 Jun 15;486(2):103-10. doi: 10.1016/j.abb.2009.04.007. Epub 2009 May 4.
Conjugated eicosapentaenoic acid (cEPA) has been found to have antitumor effects which has been ascribed to their ability to inhibit DNA topoisomerases and DNA polymerases. We here show that cEPA inhibits the catalytic activity of human topoisomerase I, but unlike camptothecin it does not stabilize the cleavable complex, indicating a different mechanism of action. cEPA inhibits topoisomerase by impeding the catalytic cleavage of the DNA substrate as demonstrated using specific oligonucleotide substrates, and prevents the stabilization of the cleavable complex by camptothecin. Preincubation of the inhibitor with the enzyme is required to obtain complete inhibition. Molecular docking simulations indicate that the preferred cEPA binding site is proximal to the active site with the carboxylic group strongly interacting with the positively charged K443 and K587. Taken together the results indicate that cEPA inhibitor does not prevent DNA binding but inhibits DNA cleavage, binding in a region close to the topoisomerase active site.
共轭二十碳五烯酸（cEPA）已被发现具有抗肿瘤作用，这归因于它们抑制DNA拓扑异构酶和DNA聚合酶的能力。我们在此表明，cEPA抑制人拓扑异构酶I的催化活性，但与喜树碱不同的是，它不会稳定可裂解复合物，这表明其作用机制不同。如使用特定寡核苷酸底物所证明的，cEPA通过阻碍DNA底物的催化裂解来抑制拓扑异构酶，并阻止喜树碱对可裂解复合物的稳定作用。抑制剂与酶预孵育是获得完全抑制所必需的。分子对接模拟表明，cEPA的优选结合位点靠近活性位点，其羧基与带正电荷的K443和K587强烈相互作用。综合这些结果表明，cEPA抑制剂不会阻止DNA结合，但会抑制DNA裂解，它结合在靠近拓扑异构酶活性位点的区域。
