Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
J Chem Phys. 2024 Oct 21;161(15). doi: 10.1063/5.0231282.
Phospholipase A2 (PLA2) catalyzes the hydrolysis of the sn-2 acyl ester linkage in phospholipid, producing lysophospholipid and fatty acid in the presence of Ca2+. The hydrolysis mediated by PLA2 has attracted much interest in various fields, such as pharmacy and biotechnology. It is recognized that PLA2 cannot hydrolyze phospholipid monolayers at high surface coverage. However, the origin of different PLA2 activities is not fully understood yet. The present study investigated the interaction between DPPC (16:0 PC) monolayer and PLA2 using heterodyne-detected sum frequency generation spectroscopy, which is interface-specific spectroscopy and highly sensitive to molecular symmetry based on a second-order nonlinear optical process. It was revealed that PLA2 adsorbs to the DPPC monolayer on the aqueous solution surface only when the surface coverage is low. The adsorption at the low surface coverage significantly changes the interfacial structures of PLA2 and the hydration, which are stabilized by the presence of Ca2+. Therefore, the restriction of the hydrolysis of phospholipid monolayers at high surface coverage can be rationalized by the inhabitation of the PLA2 adsorption. The present study deepens our molecular-level understanding of the hydrolysis of phospholipids by PLA2.
磷脂酶 A2（PLA2）在 Ca2+存在的条件下，催化磷脂 sn-2 酰基酯键的水解，生成溶血磷脂和脂肪酸。PLA2 介导的水解在药学和生物技术等各个领域引起了广泛关注。人们认识到 PLA2 不能水解高表面覆盖率的磷脂单层。然而，不同 PLA2 活性的起源尚未完全了解。本研究使用异频探测和和频产生光谱学（一种基于二阶非线性光学过程的界面特异性光谱学，对分子对称性高度敏感）研究了 DPPC（16:0 PC）单层与 PLA2 之间的相互作用。结果表明，只有在表面覆盖率低的情况下，PLA2 才会吸附在水相溶液表面的 DPPC 单层上。低表面覆盖率下的吸附显著改变了 PLA2 和水合作用的界面结构，这是由 Ca2+的存在稳定的。因此，高表面覆盖率下磷脂单层水解受限的原因可以解释为 PLA2 吸附的抑制。本研究深化了我们对 PLA2 水解磷脂的分子水平理解。
