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KMID : 0613820020120010032
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Journal of Life Science
2002 Volume.12 No. 1 p.32 ~ p.42
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Reaction Mechanism of Acetylcholinesterase Catalyzed Hydrolysis of Thiocholine Esters
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Jung Dai-Il
Choi Soon-Kyu
Lee Yong-Gyun
Park Yu-Mi
Gwak Moon-Jung
Shin Young-Ju
Choi Byung-Wook
Han Jung-Tae
Lee Bong-Ho
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Abstract
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It was researched to react horse serum-BChE with hexanoylthiocholine chosen among choline esters. According as
number of carbon of acyl group in choline esters was increased, reactivity was decreased but strength of ES complex was increased (Km=0.140mM). The pH-V/K profile for BChE-catalyzed hydrolysis of hexanoylthiocholine yields a pKa=4.974±0.028. This value is equal to recent literature that shows systematic shift from dependence of activity on the basic form fo a residue that has a pKa=6.2∼6.4 to catalysis by a residue or residues that has a pKa=4.7∼5.0. The
resulting kinetic solvent isotope effect of hexanoylthiocholine is DV/K=1.18. The magnitude of the isotope effect suggests that proton transfer is not an element of transition-state stabilization.
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KEYWORD
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horse-serum BChE, hexanoylthiocholine, kinetics, hydrolysis
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