Magnesium effect on the acetylcholinesterase inhibition mechanism: A molecular chromatographic approach

The acetylcholinesterase enzyme (AChE) was immobilized on a chromatographic support to study the effect of magnesium on the binding mechanism of five AChE inhibitors (donepezil, tacrine, galanthamine, physostigmine and huperzine). The determination of the enthalpy and entropy changes of this binding at different magnesium concentration values suggested that van der Waals interactions and hydrogen bonds predominated the donepezil and tacrine association to AChE. As well, hydrophobic and electrostatic forces seemed to be the major interactions controlling the huperzine, galanthamine and physostigmine association with AChE. In addition, it appeared that magnesium cation increased the binding affinity of galanthamine and physostigmine to the active site gorge of AChE. A comparison of the inhibitors hydrophobicity to their relative bound percentage with AChE showed an affinity enhanced with the increase in the molecule hydrophobicity and confirmed that the hydrophobic forces played an important role in the AChEI-AChE binding process. This novel biochromatographic column could be useful to find a specific inhibitor for this enzyme and so open new perspectives to be investigated.