Slow-binding inhibition of acetylcholinesterase by an alkylammonium derivative of 6-methyluracil: mechanism and possible advantages for myasthenia gravis treatment

Abstract

Inhibition of human AChE (acetylcholinesterase) and BChE (butyrylcholinesterase) by an alkylammonium derivative of 6-methyluracil, C-547, a potential drug for the treatment of MG (myasthenia gravis) was studied. Kinetic analysis of AChE inhibition showed that C-547 is a slow-binding inhibitor of type B, i.e. after formation of the initial enzyme·inhibitor complex (Ki=140 pM), an induced-fit step allows establishment of the final complex (Ki*=22 pM). The estimated koff is low, 0.05 min(-1) On the other hand, reversible inhibition of human BChE is a fast-binding process of mixed-type (Ki=1.77 μM; Ki'=3.17 μM). The crystal structure of mouse AChE complexed with C-547 was solved at 3.13 Å resolution. The complex is stabilized by cation-π, stacking and hydrogen-bonding interactions. Molecular dynamics simulations of the binding/dissociation processes of C-547 and C-35 (a non-charged analogue) to mouse and human AChEs were performed. Molecular modelling on mouse and human AChE showed that the slow step results from an enzyme conformational change that allows C-547 to cross the bottleneck in the active-site gorge, followed by formation of tight complex, as observed in the crystal structure. In contrast, the related non-charged compound C-35 is not a slow-binding inhibitor. It does not cross the bottleneck because it is not sensitive to the electrostatic driving force to reach the bottom of the gorge. Thus C-547 is one of the most potent and selective reversible inhibitors of AChE with a long residence time, τ=20 min, longer than for other reversible inhibitors used in the treatment of MG. This makes C-547 a promising drug for the treatment of this disease.

Novel conjugates of aminoadamantanes with carbazole derivatives as potential multitarget agents for AD treatment

“…Also, a typical feature of the AChE active site gorge is the presence of so-called bottleneck formed by Tyr341 and Tyr124 residues, which control the downward movement of ligands to the active site and which can be impassable for the most bulky and rigid groups53. As in many other cases, these differences between the active site gorge structures in AChE and BChE dictate the selective inhibition of these related enzymes5354. It is noteworthy that selective inhibition of BChE compared with AChE was also found for adamantyl derivatives known from the literature5556.…”

Supercomputer Modeling of Dual-Site Acetylcholinesterase (AChE) Inhibition

“…Conformations of Phe297 and Tyr124 side chains, namely, the χ 1 torsion angle for induced fit docking complexes, could be compared with conformations found in X-ray structures of human and mouse AChE and along MD trajectories for apo-AChE and AChE in complex with another bulky inhibitor [6]. We found side chain conformations from flexible docking different from those found in X-ray data or during MD simulations even with a bulky inhibitor in the gorge (Fig.…”

“…Overlaid configurations of the piperidine fragment of the γ-carboline ring of MBC and scoring were employed. MD simulations were done in 0.15 M NaCl solution with previously published methods[6,17].…”

Inhibition Effect of Ca2+ Ions on Sucrose Hydrolysis Using Invertase

“…The product pattern follows the exponential pattern, therefore, it will constant at certain time [28]. At low substrate concentration, the product obtained is linear with the inhibitor concentration [35,36]. From Figure 2, we conclude that the reducing sugar concentration decreased with the increasing of Ca 2+ ion concentration in the hydrolysis system.…”