State Key Laboratory of Food Science and Technology, Nanchang University, Jiangxi 330047, China.
School of Food Science and Technology, Dalian Polytechnic University, Dalian 116034, China.
Int J Mol Sci. 2019 Jul 12;20(14):3438. doi: 10.3390/ijms20143438.
Acyl migration (AM) is the main side reaction in the large-scale, regio-specific lipase catalyzed production of structural triglycerides (STs). A detailed understanding of the mechanism of AM was obtained during the process of lipase-catalyzed schemes (LCSs), which play a vital role in improving the quality and total yield of STs. However, currently, the mechanism of AM remains controversial. Herein, the two mechanisms (non-catalyzed (NCM) and lipase-catalyzed (LCM)) of AM have been analyzed in detail by the density functional theory (DFT) at the molecular level. Based on the computational results, we concluded that the energy barrier of the rate-limiting step in the LCM was 18.8 kcal/mol, which is more in agreement with the available experimental value (17.8 kcal/mol), indicating that LCM could significantly accelerate the rate of AM, because it has an energy barrier ~2 times lower than that of the NCM. Interestingly, we also found that the catalytic triad (Asp-His-Ser) of the lipase and water could effectively drop the reaction barrier, which served as the general acid or base, or shuttle of the proton.
酰基迁移（AM）是大规模、区域特异性脂肪酶催化结构三酰基甘油（ST）生产中的主要副反应。在脂肪酶催化方案（LCS）过程中，对 AM 机制的详细了解对提高 ST 的质量和总产率起着至关重要的作用。然而，目前 AM 的机制仍存在争议。本文在分子水平上通过密度泛函理论（DFT）详细分析了 AM 的两种机制（非催化（NCM）和脂肪酶催化（LCM））。基于计算结果，我们得出结论，LCM 中限速步骤的能垒为 18.8 kcal/mol，与可用的实验值（17.8 kcal/mol）更吻合，表明 LCM 可以显著加速 AM 的速率，因为它的能垒比 NCM 低约 2 倍。有趣的是，我们还发现脂肪酶的催化三联体（Asp-His-Ser）和水可以有效地降低反应能垒，起到广义酸或碱或质子穿梭的作用。
