Yonezawa Yuko, Tsuzuki Tsuyoshi, Eitsuka Takahiro, Miyazawa Teruo, Hada Takahiko, Uryu Keisuke, Murakami-Nakai Chikako, Ikawa Hiroshi, Kuriyama Isoko, Takemura Masaharu, Oshige Masahiko, Yoshida Hiromi, Sakaguchi Kengo, Mizushina Yoshiyuki
Laboratory of Food and Nutritional Sciences, Department of Nutritional Science, Kobe-Gakuin University, Nishi-ku, Kobe, Hyogo 651-2180, Japan.
Arch Biochem Biophys. 2005 Mar 1;435(1):197-206. doi: 10.1016/j.abb.2004.12.011.
DNA topoisomerases (topos) and DNA polymerases (pols) are involved in many aspects of DNA metabolism such as replication reactions. We reported previously that long chain unsaturated fatty acids such as polyunsaturated fatty acids (PUFA) (i.e., eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA)) inhibited the activities of eukaryotic pols in vitro. In the present study, we found that PUFA also inhibited human topos I and II activities, and the inhibitory effect of conjugated fatty acids converted from EPA and DHA (cEPA and cDHA) on pols and topos was stronger than that of normal EPA and DHA. cEPA and cDHA inhibited the activities of mammalian pols and human topos, but did not affect the activities of plant and prokaryotic pols or other DNA metabolic enzymes tested. cEPA was a stronger inhibitor than cDHA with IC(50) values for mammalian pols and human topos of 11.0-31.8 and 0.5-2.5 microM, respectively. Therefore, the inhibitory effect of cEPA on topos was stronger than that on pols. Preincubation analysis suggested that cEPA directly bound both topos I and II, but did not bind or interact with substrate DNA. This is the first report that conjugated PUFA such as cEPA act as inhibitors of pols and topos. The results support the therapeutic potential of cEPA as a leading anti-cancer compound that poisons pols and topos.
DNA拓扑异构酶（拓扑酶）和DNA聚合酶（聚合酶）参与DNA代谢的许多方面，如复制反应。我们之前报道过，长链不饱和脂肪酸，如多不饱和脂肪酸（PUFA）（即二十碳五烯酸（EPA）和二十二碳六烯酸（DHA））在体外可抑制真核聚合酶的活性。在本研究中，我们发现PUFA也抑制人拓扑酶I和II的活性，并且由EPA和DHA转化而来的共轭脂肪酸（cEPA和cDHA）对聚合酶和拓扑酶的抑制作用强于正常的EPA和DHA。cEPA和cDHA抑制哺乳动物聚合酶和人拓扑酶的活性，但不影响所测试的植物和原核聚合酶或其他DNA代谢酶的活性。cEPA是比cDHA更强的抑制剂，其对哺乳动物聚合酶和人拓扑酶的IC50值分别为11.0 - 31.8和0.5 - 2.5微摩尔。因此，cEPA对拓扑酶的抑制作用强于对聚合酶的抑制作用。预孵育分析表明，cEPA直接与拓扑酶I和II结合，但不与底物DNA结合或相互作用。这是关于共轭PUFA如cEPA作为聚合酶和拓扑酶抑制剂的首次报道。这些结果支持了cEPA作为一种能毒害聚合酶和拓扑酶的主要抗癌化合物的治疗潜力。
