分子动力学模拟分析超高压对固液两态多酚氧化酶稳定性的影响

Effect of Ultra-High Pressure on the Stability of Polyphenol Oxidase in the Solid and Liquid States Analyzed by Molecular Dynamics Simulation

以固态晶体(crystal,C-)、液态(liquid,L-)多酚氧化酶(polyphenol oxidase,PPO)为对象,采用分子动力学模拟的方法,分析其在常温(298.15 K)常压/高压(0.1~400.0 MPa)条件下分子构象的变化。结果表明:固液两态PPO的空间结构均随压力(0.1~400.0 MPa)增大而变的不稳定;与L-PPO相比,C-PPO对压力更敏感,表现出更高的残基波动,溶剂可及表面积和体积减小,蛋白结构更致密;α-螺旋向无规卷曲过渡,导致氢键数量不稳定,螺旋弹性也降低,整体构象差异明显;活性位点Cu^(2+)位置疏远,残基之间距离发生改变、运动出现随机化,干扰底物催化结合。因此,物理状态和压力改变PPO空间结构、残基运动模式和底物结合范围,影响酶稳定性。因此,PPO状态和压力因素对酶变性程度可排序为:固态>液态,物理状态>压力水平。

This study evaluated the conformational changes of polyphenol oxidase(PPO)in the crystalline solid(C-)and liquid(L-)states at room temperature(298.15 K)and normal or ultra-high pressure(0.1-400.0 MPa).The results indicated that when the pressure increased from 0.1 to 400.0 MPa,the spatial structure of PPO in both states became unstable.Compared with L-PPO,C-PPO was more susceptible to pressure,and exhibited higher residue fluctuations,reduced solvent accessible surface area and volume and a denser structure.With the transition ofα-helices to random coils under high pressure conditions,the number of hydrogen bonds became unstable andα-helix elasticity decreased,thus leading to significant conformational differences.The active site of the Cu^(2+)position was displaced,the inter-residue distance was altered and random motion appeared,thereby interfering with substrate binding.In conclusion,both physical state and pressure level can influence PPO’s spatial structure,residue mobility,and substrate binding range,ultimately impacting the enzyme’s stability,and their impacts on the degree of enzyme denaturation can be ranked as follows:solid state>liquid state,and physical state>pressure level.