College of Biological and Chemical Engineering, Anhui Polytechnic University, Wuhu 241000, PR China.
Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan 250011, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2019 Jul 5;218:51-61. doi: 10.1016/j.saa.2019.03.109. Epub 2019 Apr 1.
α-Glucosidase (AG) is an important drug target for the treatment of type 2 diabetes mellitus in humans due to the potential effect of down regulating glucose absorption in patients. In our previous study, salvianolic acid A (SAA) was found to exhibit potent AG inhibitory activity, whereas the interaction mechanism was still ambiguous. Herein, the interaction mechanism of SAA and AG was investigated by multi-spectroscopic methods along with molecular docking. As a result, it was found that SAA reversibly inhibited AG in a competitive manner with IC of 16.44 ± 0.18 μM, and the inhibition belonged to a multi-phase kinetics process with a first-order reaction. The intrinsic fluorescence of AG could be strongly quenched by SAA through a static quenching mechanism. The negative Gibbs free energy change and positive values of enthalpy and entropy change revealed that the binding of SAA to AG was spontaneous and dominated mainly by hydrophobic interactions, and only a single binding site was determined for them. Analysis of synchronous fluorescence, ANS-binding fluorescence, circular dichroism and Fourier transform infrared spectra suggested that the binding of SAA to AG induced rearrangement and conformational changes of the enzyme. Besides, further molecular modelling validated that SAA could bind to the active domain and prevent the entrance of substrate, resulting in the inhibition of AG activity. These findings provide new insights into understanding the interaction mechanism of SAA on AG.
α-葡萄糖苷酶（AG）是人类 2 型糖尿病治疗的重要药物靶点，因为它具有降低患者葡萄糖吸收的潜力。在我们之前的研究中，发现丹酚酸 A（SAA）具有很强的 AG 抑制活性，但其相互作用机制仍不清楚。本研究采用多种光谱方法结合分子对接研究了 SAA 与 AG 的相互作用机制。结果表明，SAA 以竞争性方式可逆地抑制 AG，IC 为 16.44±0.18μM，抑制属于一级反应的多相动力学过程。SAA 通过静态猝灭机制强烈猝灭 AG 的固有荧光。负的吉布斯自由能变化和正的焓和熵变化值表明，SAA 与 AG 的结合是自发的，主要由疏水相互作用主导，并且确定它们之间只有一个结合位点。同步荧光、ANS 结合荧光、圆二色性和傅里叶变换红外光谱分析表明，SAA 与 AG 的结合诱导了酶的重排和构象变化。此外，进一步的分子建模验证了 SAA 可以结合到活性域并阻止底物的进入，从而抑制 AG 的活性。这些发现为理解 SAA 对 AG 的相互作用机制提供了新的见解。
