Binding of huperzine A and galanthamine to acetylcholinesterase, based on ONIOM method

Binding energy calculations of huperzine A (HUP A) and galanthamine (GAL) to the binding pocket of the acetylcholinesterase enzyme (AChE) were studied. It was found that hydrogen bond formation and particular hydrogen π interactions exhibit the most significant contributions to the binding interaction of HUP A with Trp84 (W84) and Tyr130 (Y130), whereas no hydrogen bond was detected with Y130 of GAL binding. The interaction energies, calculated at the MP2 level between drugs and residues, demonstrate that the attractive interactions between GAL and residues at positions 84 and 130 were less than those for HUP A by 1.6 and 7.7 kcal·mol(-1), respectively. In addition, ONIOM3 results show that the binding energies of HUP A per pocket (-28.4 kcal mol(-1)) are higher than for GAL per pocket (-17.0 kcal·mol(-1)). The detailed understanding of these interactions can be useful for the design of specific inhibitors for the AChE binding site.The more efficient and specific inhibition of acetylcholinesterase may provide an enhanced treatment strategy in Alzheimer's disease compared to the currently available inhibitors. This study discusses interactions of the enzyme binding site with two ligands. The results may pave the way to the development of more potent inhibitors.