甲醇辅助的半胱氨酸乙酰化反应的密度泛函理论研究

运用密度泛函理论（Density Functional Theory）中的B3LYP方法在6—31G^＊基组水平上，研究了硫醇枯草杆菌蛋白酶（Th—Subt）活性中心的半胱氨酸（Cys）残基与底物乙酸乙酯的转乙酰基反应，并与甲醇分子辅助的乙酰基转移过程作了比较．计算结果表明，该反应有两种可能的反应路径：协同反应和分步反应．后者在竞争中占优势，是势能面上的最低能量反应通道．当甲醇分子辅助反应时，反应路径的优先次序并未发生改变，但活化势垒大大降低，降幅为38．1—85．9kJ／mol．此结果证实了实验得出的结论．

A DFT Study on the Mechanism of Methanol-Assisted Cysteine Acetylation

The acetyltransfer mechanism of the active site cysteine residue and the acetyl donor, ethyl acetate, was investigated by Density Functional Theory （DFT） B3LYP at 6-31G^＊ basis level. Furthermore, the process was compared with that of the methanol-assisted acetylation. The results indicated that this reaction could be achieved through two possible reaction pathways： one was concerted and the other was stepwise, and the latter was the minimum energy pathway on the potential energy surface due to the lower activation energy barriers. The assistance of one methanol molecule in the transition state can obviously decrease the energy barrier at a range of 38. 1 to 85.9 kJ/mol, but the priority for the pathways still remained. All the results were consistent with the experimental data very well.