Evaluation and Characterization of Free and Immobilized Acethylcholinesterase with Fluorescent Probe, Differential Scanning Calorimetry and Docking

Acetylcholinesterase (AChE) enzyme which catalyses the hydrolysis of choline esters, such as acetylcholine, is very important in nerve function. Previous structural studies showed the possible amyloid fibril formation on the AChE. Therefore it is important to understand interaction of ligands to prevent the formation of  amyloid fibrils. The purpose of the present study was to  characterize AChE structure using differential scanning calorimetry (DSC), fluorescent probe and docking methods. Immobilization of AChE was carried out on porous silica matrix. Fluorescence of free and immobilized form of AChE was measured by a spectrofluorometer at 435 nm excitation wavelength .Calorimetric measurements were carried out on a differential scanning calorimeter. AChE–ligand docking Version Lig plot was used for docking studies. Based on our data, thioflavin T (Th-T) binding to the peripheral site of AChE, increased its fluorescence in a dose-dependent manner. DSC showed that immobilized AChE form is probably more stable structurally than its free form. Protein docking study revealed that AChE interacts through different regions with matrix, and each of these interactions have its own binding energy. A comparison between DSC, fluorescence spectroscopy and docking results revealed excellent agreement between them.