Inactivation of acetylcholinesterase by various fluorophores

Abstract

The inhibition of recombinant mouse acetylcholinesterase (rMAChE) and electric eel acetylcholinesterase (EEAChE) by seven, structurally different chromophore-based (dansyl, pyrene, dabsyl, diethylamino- and methoxycoumarin, Lissamine rhodamine B, and Texas Red) propargyl carboxamides or sulfonamides was studied. Diethylaminocoumarin, Lissamine, and Texas Red amides inhibited rMAChE with IC₅₀ values of 1.00 μM, 0.05 μM, and 0.70 μM, respectively. Lissamine and Texas Red amides inhibited EEAChE with IC₅₀ values of 3.57 and 10.4 μM, respectively. The other chromophore amides did not inhibit either AChE. The surprising inhibitory potency of Lissamine was examined in further detail against EEAChE and revealed a mixed-type inhibition with K_i = 11.7 μM (competitive) and K_i′ = 24.9 μM (noncompetitive), suggesting that Lissamine binds to free enzyme and enzyme–substrate complex.

Keywords::

• Acetylcholinesterase
• fluorophores
• inhibition
• Lissamine
• mixed-type inhibition

Acknowledgments

The research in this study was supported by a grant to one of the authors (C.M.T.) (NIH UO1-ES016102). The authors are grateful for the support of the Core Laboratory for Neuromolecular Production (NIH P30-NS055022) and the Center for Structural and Functional Neuroscience (NIH P20-RR015583).

Declaration of interest: The authors report no conflicts of interest.