中文摘要：

甘草次酸（glycyrrhetinic acid,GA）是甘草主要活性组分,可诱导肿瘤细胞凋亡,抑制肿瘤细胞生长.然而,其对BLM解旋酶的抑制作用尚未见报道.本文注视甘草次酸对BLM解旋酶构象、二级结构和生化活性的影响.圆二色光谱和紫外光谱分析显示,GA可破坏BLM642-1290解旋酶α-螺旋结构,改变其构象,并具有2个结合位点.采用荧光偏振技术和自由磷检测证明,GA以浓度依赖的方式抑制BLM642-1290解旋酶与底物dsDNA及ssDNA的结合,抑制BLM642-1290解旋酶活性及ATP酶活性,且抑制类型为混合抑制.综上所述,本文证明GA可通过结合BLM解旋酶,改变BLM解旋酶构象,抑制BLM解旋酶与DNA的结合,从而抑制BLM解旋酶的生化活性.我们的发现将对深入认识GA的抗肿瘤作用有新的启示.

英文摘要：

Glycyrrhetinic acid（GA） is a major active constituent of glycyrrhiza, which can induce tumor cell apoptosis, inhibiting tumor cell growth. However, the inhibition of BLM helicase by GA has not yet been reported. Herein, we focus the effects of GA on BLM helicase conformation, secondary structure and biochemical properties. The circular dichroism（CD） spectra and ultraviolet spectrum（UV） showed that GA can destroyed the or-helix structure and changed the conformation of BLM642-1290 helicase, there were two binding sites. Fluorescence anisotropy technology and free phosphorus detection demonstrated that the DNA-binding（dsDNA or ssDNA） , helicase and ATPase activity of BLM642-1290 helicase were inhibited by GA with a concentration dependence, indicating that the inhibition is mixed. Taken together, we have demonstrated that GA combinning with BLM642-1290 helicase can change the conformation of BLM642-1290 helicase, inhibit the combine with DNA, and further inhibit the biochemical properties of BLM642-1290 helicase. Our finding may provide further insight into the anti-tumor effect of GA.