分子动力学模拟与热稳定性实验相结合分析乙酰氨基葡萄糖与脂肪酶的相互作用机制

Molecular Dynamics Simulation Combined with Thermal Stability Experiments to Analyze the Interaction Mechanism between Acetylglucosamine and Lipase

摘要:

该研究采用分子动力学模拟方法研究南极假丝酵母脂肪酶B（CaLB）与乙酰氨基葡萄糖（GlcNAc）的相互作用，以及通过热稳定性实验论证GlcNAc对CaLB的保护效果。结果表明：在323.15 K下，CaLB与GlcNAc的静电势能与Lennard-Jones（L-J）在前20 ns模拟时间中显著下降，CaLB-250 mmol/L-GlcNAc模型在0~100 ns时，静电势能和L-J势能分别下降了3350 kJ/mol和2791 kJ/mol，二者间的氢键数从0增加到115左右，CaLB与GlcNAc的可及面积（SASA）接近于50 nm2。均方根偏差（RMSD）和均方根波动（RMSF）数据表明：游离酶（Free-CaLB）模型在323.15 K和353.15 K下的RMSD分别为0.2617 nm和0.3473 nm，而不同浓度CaLB-GlcNAc模型的RMSD均小于Free-CaLB的数值，且CaLB-GlcNAc组装体模型区域（Val 147-Leu 155）波动明显小于Free-CaLB模型，说明GlcNAc可以减弱Free-CaLB的韧性而有效维持脂肪酶的原始结构。热稳定性实验表明：Free-CaLB及CaLB-GlcNAc在60 ℃下处理2.0 h，Free-CaLB的残余酶活力仅为22.26%，而CaLB-GlcNAc的残余酶活力为52.11%。综上，乙酰氨基葡萄糖可以提高游离脂肪酶的热稳定性。

Abstract:

In this study, molecular dynamics simulation was used to examine the interaction between Candida Antarctica Lipase B (CaLB) and acetylglucosamine (GlcNAc), and demonstrate the protective effect of GlcNAc on CaLB through thermal stability experiments. The results show that at 323.15 K, the electrostatic potential energy of CaLB and GlcNAc as well as Lennard-Jones (L-J) decreased significantly in the first 20 ns simulation time. When the CaLB-250 mmol/L-GlcNAc model was at 0~100 ns, the electrostatic potential energy and LJ potential energy decreased by 3350 kJ/mol and 2791 kJ/mol, respectively, and the number of hydrogen bonds between them increased from 0 to about 115. The accessible area (SASA) of CaLB and GlcNAc is close to 50 nm2. The root mean square deviation (RMSD) and root mean square fluctuation (RMSF) data show that the RMSD of the Free-CaLB model at 323.15 K and 353.15 K were 0.2617 nm and 0.3473 nm, respectively, while the RMSF of the CaLB-GlcNAc model at different concentrations was smaller than that of Free-CaLB, and the fluctuation of the CaLB-GlcNAc assembly model region (Val 147-Leu 155) was significantly smaller than that of the Free-CaLB model, indicating that GlcNAc can weaken the toughness of Free-CaLB and maintain effectively the original structure of CaLB. Thermal stability experiments showed that: after Free-CaLB and CaLB-GlcNAc were treated at 60 ℃ for 2.0 h, the residual enzyme activity of Free-CaLB was only 22.26%, whilst the residual enzyme activity of CaLB-GlcNAc was 52.11%. In summary, the thermal stability of Free-CaLB can be improved by acetylglucosamine.