BioResearch Lab, Faculty of Biological Sciences, Shahid Beheshti University, G.C. Tehran, Iran.
Eur J Pharmacol. 2010 Jun 10;635(1-3):23-6. doi: 10.1016/j.ejphar.2010.02.040. Epub 2010 Mar 15.
Scopolamine (hyoscine) is commonly used as an anticholinergic drug to relieve nausea, vomiting and dizziness of a motion sickness as well as recovery from anesthesia and surgery. Sucrase as a hydrolytic enzyme breaks down sucrose into its monomers, glucose and fructose. The aim of this study was to evaluate the effect of scopolamine on the activity and the structural changes of yeast sucrase. The results showed that binding of scopolamine to sucrase could inhibit the enzyme activity. A non-competitive inhibition was observed in different concentrations of scopolamine (0.6 to 3.6mM). The study by circular dichroism measurement in far-UV showed that the absolute enzyme exhibited a flat negative trough, indicating the presence of alpha-helices and beta-sheet structures in the enzyme. Binding of the inhibitor on the enzyme made a deeper trough at 218nm, suggesting the increasing of beta-sheet content of the enzyme. Fluorescence measurement showed that binding of scopolamine to free enzyme and enzyme-substrate complex increased the peak intensity at 350nm and also induced red shift. Our findings suggest that scopolamine binds to the location other than the active site of enzyme and that the binding causes structural changes and inhibits the enzyme activity.
莨菪碱（天仙子胺）通常被用作一种抗胆碱能药物，以缓解晕动病的恶心、呕吐和头晕，以及麻醉和手术的恢复。蔗糖酶是一种水解酶，将蔗糖分解成其单体葡萄糖和果糖。本研究旨在评估莨菪碱对酵母蔗糖酶活性和结构变化的影响。结果表明，莨菪碱与蔗糖酶的结合可以抑制酶活性。在不同浓度的莨菪碱（0.6 至 3.6mM）下观察到非竞争性抑制。圆二色性远紫外测量研究表明，绝对酶呈现平坦的负谷，表明酶中存在α-螺旋和β-折叠结构。抑制剂与酶的结合在 218nm 处形成更深的谷，表明酶的β-折叠含量增加。荧光测量表明，莨菪碱与游离酶和酶-底物复合物的结合增加了 350nm 处的峰强度，并诱导了红移。我们的研究结果表明，莨菪碱结合在酶的活性位点以外的位置，结合导致结构变化并抑制酶活性。
