The Deacylation Step of Acetylcholinesterase: Computer Simulation Studies
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- 作者：Peter Vagedes ; Bjö ; rn Rabenstein ; Johan Å ; qvist ; John Marelius ; and Ernst-Walter Knapp
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：December 13, 2000
- 年：2000
- 卷：122
- 期：49
- 页码：12254 - 12262
- 全文大小：119K
- 年卷期：v.122,no.49(December 13, 2000)
- ISSN：1520-5126
文摘
The deacylation step of acetylcholinesterase was simulated using the empirical valence bond (EVB)method in combination with free energy perturbation calculations. Before the enzyme structure was used tosimulate the reaction, the protonation pattern of the acylated enzyme and the free enzyme was determined bya Monte Carlo titration. As a result, it was found that Glu199, which is located close to the catalytic triad, isprotonated in the free and acylated enzyme. Also, the EVB simulation of the reaction showed that the unchargedGlu199 is favorable to stabilize the transition state of the deacylation step. This is in agreement with experimentsdemonstrating that the Glu199Gln mutation does not have a significant influence on the kinetics of deacylation.The EVB calculations yielded an energy barrier of the deacylation step that is 11-12 kcal/mol lower in AChEas compared to a reference reaction in water. The largest calculated rate of the deacylation reaction is kcat =5.5 × 102 s-1 and thus only by a factor of 30 smaller than the experimental value.