光谱法比较喜树碱与溶菌酶、过氧化氢酶的相互作用

Spectroscopic Comparison of the Interactions of Camptothecin with Lysozyme and Catalase

采用紫外可见吸收、红外、荧光等多种光谱学方法研究了抗癌药物喜树碱和溶菌酶及过氧化氢酶两种蛋白之间的相互作用,结果表明,喜树碱与之均形成基态复合物并引起蛋白内源荧光猝灭。通过计算确定了喜树碱和蛋白相互作用的结合常数、结合位点数、主要作用力类型以及与蛋白中色氨酸的结合距离。喜树碱对过氧化氢酶具有较高的结合能力,这主要是由于喜树碱不仅与过氧化氢酶中的色氨酸存在相互作用,也与酶中的酪氨酸及血红素产生相互作用。喜树碱的存在可引起蛋白构象发生变化,使α-螺旋二级结构减少。

The interactions of an anticancer drug, camptothecin with lysozyme and catalase were investigated by the combination of several spectroscopic techniques, including UV - Vis absorption, IR and fluorescence spectra. The results showed that camptothecin could form groundstate complexes with these two proteins and induce the quenching of the intrinsic fluorescence of proteins. The binding constants and the numbers of binding site of camptothecin interacting with lysozyme and catalase at different temperatures were calculated. Their main binding forces were electrostatic interaction and hydrophobic interaction. The distances between camptothecin and tryptophan residues in lysozyme and catalase were determined. Camptothecin showed a higher binding affinity on catalase than it had on lysozyme, as it interacted not only with tryptophan residue, but also with tyrosine residue and heine in catalase. The results also showed that the presence of camptothecin could induce the conformational variation of proteins with a decrease in a-helix secondary structure.