Slow-Binding Inhibition of Acetylcholinesterase by a 6-Methyluracil Alkyl-Ammonium Derivative: Mechanism and Advantages for Myasthenia Gravis Treatment.Kharlamova, A.D., Lushchekina, S.V., Petrov, K.A., Kots, E.D., Nachon, F.V., Villard-Wandhammer, M., Zueva, I.V., Krejci, E., Reznik, V.S., Zobov, V.V., Nikolsky, E.E., Masson, P.
(2016) Biochem.J. 473: 1225
- PubMed: 26929400
- DOI: 10.1042/BCJ20160084
- PubMed 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 sh ...
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.
A.E. Arbuzov Institute of Organic and Physical Chemistry of Russian Academy of Sciences, Arbuzov Str. 8, Kazan 420088 Russia.