1-脱氧野尻霉素对α-葡萄糖苷酶的抑制作用机制

Mechanism for the Inhibitory Effect of 1-Deoxynojirimycin on α-Glucosidase

运用紫外光谱法、荧光光谱法和圆二色光谱法,研究桑叶提取物1-脱氧野尻霉素(1-deoxynojirimycin,DNJ)对α-葡萄糖苷酶的作用。结果发现:DNJ与α-葡萄糖苷酶反应的半抑制浓度为0.297μg/mL,作用类型为竞争型抑制;其与α-葡萄糖苷酶主要通过静电吸引力相互作用形成基态复合物,并使α-葡萄糖苷酶的内源荧光猝灭;DNJ与α-葡萄糖苷酶相互作用形成复合物的过程是熵驱动的吸热反应,静电吸引力是两者结合反应的主要驱动力。不同温度(273、298、310 K)条件下荧光猝灭常数(K_(sv))分别为1.48×10~4、1.29×10~4、1.12×10~4 L/mol。DNJ使α-葡萄糖苷酶的构象发生变化,且使其二级结构重新排列;诱导酶活性口袋关闭,不利于底物结合到活性位点,推测这可能是DNJ抑制α-葡萄糖苷酶活性从而降低血糖水平的机理。

The inhibitory effect of 1-deoxynojirimycin(DNJ)extracted from mulberry leaves onα-glycosidase was investigated by ultraviolet,fluorescence and circular dichroism(CD)spectroscopy.As a result,the half maximum inhibitory concentration(IC50)of DNJα-glucosidase was 0.297μg/mL.The type of inhibition was competitive.DNJ interacted withα-glucosidase through electrostatic attraction generating ground-state complexes and resulting in endogenous fluorescence quenching ofα-glucosidase.The formation process of DNJ-α-glucosidase complexes was an entropy-driven endothermic reaction.The interaction was mainly driven by electrostatic attraction forces.At different temperatures(273,298 and 310 K),fluorescence quenching constants(Ksv)were 1.48×10^4,1.29×10^4,and 1.12×10^4 L/mol,respectively.DNJ resulted in a conformational change ofα-glucosidase and rearrangement of the secondary structure inducing closing of the enzyme active pocket and consequently inhibiting substrate binding to the active center.These findings may explain the mechanism by which DNJ inhibitedα-glucosidase activity and thus reduced blood glucose levels.