槲皮素对酪氨酸酶的抑制作用与分子机理

Inhibitory Effect of Quercetin on Tyrosinase and Its Molecular Mechanism

摘要:

本文以L-多巴为底物，采用酶抑制动力学法研究了槲皮素对酪氨酸酶的抑制作用大小及类型，并采用荧光光谱技术分析其与酪氨酸酶的猝灭作用类型、结合位点、作用力类型。在此基础上，进一步利用柔性分子对接技术分析槲皮素对酪氨酸酶的抑制机理。结果表明，槲皮素对酪氨酸酶具有抑制作用，抑制常数KI为36 mM，以竞争性抑制剂形式抑制酪氨酸酶活性，是一种可逆性抑制剂；槲皮素以1:1比例通过氢键和疏水作用力结合于酪氨酸酶活性中心，且对酪氨酸酶的荧光产生静态淬灭作用，具有氢键及疏水作用力；分子对接结果验证了以上实验结论：槲皮素占据了酪氨酸酶活性中心，且与活性中心部位的Asn260和Gly62残基形成了强烈的氢键作用，同时伴有疏水作用共同稳定复合物的结构。

Abstract:

The type and intensity of the inhibitory effect of quercetin on tyrosinase were studied using enzyme inhibition kinetics with L-dopa as a substrate. The type of fluorescence quenching, binding sites, and the type of interaction between quercetin and tyrosinase were analyzed using fluorescence spectroscopy. Furthermore, the molecular mechanism of the inhibitory effect was investigated using flexible molecular docking. The results showed that quercetin inhibited the activity of tyrosinase with an inhibitor constant (KI) of 36 mM. Quercetin can be regarded as a competitive and reversible inhibitor of tyrosinase. Quercetin bound to the active site of tyrosinase via hydrophobic interactions and hydrogen bonds at a ratioof 1 : 1, and quenched the fluorescence of tyrosinase by static quenching. Concomitantly, molecular docking results confirmed that quercetin occupied the active site of tyrosinase and formed strong hydrogen bonds with residues Asn260 and Gly62 located at the active site of tyrosinase. Moreover, hydrophobic interaction played a key role in stabilizing the structure of the complex formed.