A Density Functional Theory (DFT) Study of the Acyl Migration Occurring during Lipase-Catalyzed Transesterifications

• Published in: International journal of molecular sciences Vol. 20; no. 14; p. 3438
• Main Authors: Mao, Jinyuan, Hu, Zhenying, Hu, Jiangning, Zhu, Xuemei, Xiong, Hua
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 12-07-2019; MDPI
• Subjects: Acetic acid; acyl migration; Catalysis; Catalysts; Chemical Phenomena; Density Functional Theory; Energy; Enzymes; Equilibrium; Esterification; Ethanol; Fatty acids; Hydrogen bonding; Hydrogen bonds; Hypotheses; Imidazole; Influence; Lipase; Lipase - chemistry; lipase-catalyzed mechanism; Models, Chemical; Models, Molecular; Molecular Structure; Oils & fats; Reaction time; Solvents; structural triglycerides; Triglycerides - chemistry; Water chemistry; acyl migration; lipase-catalyzed mechanism; structural triglycerides; QM; density functional theory
• ISSN: 1422-0067; 1661-6596; 1422-0067
• 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.