Phospholipases are important probes for understanding structure–function relationships of membrane proteins. Many neurotoxins have phospholipase activity, and they have been recognized to be potential therapeutic agents for biological warfare. Understanding the modes of action of these enzymes is important for the development of effective therapeutic strategies. Human secretory phospholipases A2 (sPLA₂) interact with cellular membranes and catalyze the hydrolysis of phosphate ester bonds of phospholipids. The activity of these enzymes increases tremendously upon binding to a hydrophobic interface. Using molecular dynamics (MD) simulations in implicit solvent and membrane environments, we investigated alterations in structure and conformation of human sPLA₂ upon its interaction with a membrane that may be associated with the activation of the enzyme. In 50 ns MD simulations, starting from six different initial orientations of the protein relative to the membrane surface, the enzyme consistently adopted a membrane-bound configuration in close agreement with the known experimental data. The simulations also reproduced the experimentally determined distribution of hydrophobic and polar side chains on the interfacial binding surface. Differences in the dynamic behavior of the enzyme between the solvent and membrane-bound states were observed. In nonpolar media, the enzyme underwent major conformational rearrangements, which exposed the active site to the membrane. The increased mobility of the surface loop and the β-wing regions is required for the conformational change, which is essentially induced by the movement of N-terminal helix. Several active site residues underwent structural changes that reorganize the binding site for substrate catalysis. Overall, the results provided a valuable insight into the interfacial behavior of sPLA₂ enzyme and suggested that membrane binding is essential but insufficient for sPLA₂ activation.

磷脂酶是了解膜蛋白结构与功能关系的重要探针。许多神经毒素具有磷脂酶活性，并且它们被认为是生物战的潜在治疗剂。了解这些酶的作用方式对于开发有效的治疗策略很重要。人分泌型磷脂酶A2（sPLA ₂）与细胞膜相互作用，并催化磷脂的磷酸酯键水解。这些酶的活性在与疏水性界面结合后大大增加。使用隐式溶剂和膜环境中的分子动力学（MD）模拟，我们研究了人类sPLA ₂结构和构象的变化当它与可能与酶活化有关的膜相互作用时。在50 ns的MD模拟中，从蛋白质相对于膜表面的六个不同初始方向开始，该酶始终采用与已知实验数据非常一致的膜结合构型。该模拟还再现了界面结合表面上疏水和极性侧链的实验确定分布。观察到了溶剂和膜结合状态之间酶动力学行为的差异。在非极性介质中，酶发生主要构象重排，使活性位点暴露于膜。为了改变构象，需要增加表面环和β-翼区的迁移率，这主要是由N末端螺旋的运动引起的。几个活性位点残基发生结构变化，这些结构重组了结合位点以进行底物催化。总体而言，结果为sPLA的界面行为提供了宝贵的见解₂酶，提示膜结合是必不可少的，但不足以激活sPLA ₂。