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Ligand stabilization of cholinesterases
C S Payne1, M Saeed, A D Wolfe
1Department of Applied Biochemistry, Walter Reed Army Institute of Research, Washington, DC.
Biochimica Et Biophysica Acta
|November 9, 1989
Summary
Ligands and inhibitors stabilize acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) against denaturation. Stabilization effectiveness varied by ligand, suggesting a common mechanism involving the active center
Area of Science:
- Biochemistry
- Enzymology
- Pharmacology
Background:
- Cholinesterases, including acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), are crucial enzymes in neurotransmission.
- Understanding their stability is vital for developing effective therapeutic agents and understanding enzyme mechanisms.
Purpose of the Study:
- To investigate the stabilization effects of various ligands and inhibitors on fetal bovine serum acetylcholinesterase (FBS AChE) and human butyrylcholinesterase (BuChE) under physical and chemical stress.
- To elucidate the mechanism of stabilization by analyzing the relationship between ligand properties and enzyme stability.
Main Methods:
- Enzyme denaturation studies were conducted across a temperature range of 50-56°C.
- The stabilizing effects of different ligands and inhibitors were assessed as a function of temperature, concentration, and time.
- Urea-induced denaturation was also employed to evaluate ligand effects.
Main Results:
- AChE denaturation followed a binary exponential function, with a diminishing slower fraction at higher temperatures.
- Ligands and inhibitors significantly stabilized both AChE and BuChE, with varying efficacy.
- Rank order of stabilization for AChE: edrophonium > decamethonium > pralidoxime chloride > procainamide. For BuChE: decamethonium > procainamide > edrophonium > pralidoxime.
- A linear relationship was observed between the fast/slow ratio and the log of the 50% inhibitory concentration (I50) for protective ligands, indicating stabilization via the active center's anionic site.
- Ligands also retarded urea-induced cholinesterase denaturation.
Conclusions:
- Ligands and inhibitors effectively stabilize cholinesterases against thermal and chemical denaturation.
- The stabilization mechanism appears to involve the active site's anionic region, as evidenced by the correlation with inhibitory concentrations.
- These findings provide insights into cholinesterase structure-activity relationships and potential therapeutic strategies.