Structural Change and Activity Control of Peptides and Proteins in Biomembranes Including Boundary Lipids

磷脂酸（PA）、磷脂酰肌醇（PI）和鞘磷脂（SpM）等酸性磷脂被认为是通过与生物膜中蛋白质的强相互作用而起“边界脂”的作用。这些脂类也影响生物膜中磷脂酰胆碱（PC）的取向。本项目的目的是了解“边界脂”对生物膜中多肽和蛋白质的结构和活性的影响。本项目选择脂氧合酶（LOX）作为靶蛋白，因为这种酶已知在水和脂质界面起作用。研究了边界脂的加入对液滴和囊泡界面液态氧活性的影响。在囊泡分散体和乳剂中添加PA和脂肪酸可显著提高LOX的活性。动力学分析和ζ电位测量表明，液氧活性的提高是由于液氧通过静电相互作用对界面的吸附力增加。动态光散射、电子显微镜和^<31 b> P-NMR分析表明，PA和脂肪酸的加入诱导PC囊泡膜形成六角形结构和胶束状颗粒。这些结果表明，“边界脂质”通过修饰膜结构来控制酶的活性。

Acidic phospholipids such as phophatidic acid (PA) and Phosphatidylinositol (PI) and Sphingomyelin (SpM) are believed to act as "boundary lipids" via strong interaction with proteins in biomembranes. These lipids also affect the orientation of phosphatidylcholine (PC) in biomembranes. The purpose of this project is to understand the effects of "boundary lipids" on the structure and activity of peptides and proteins in biomembranes.In this project, lipoxygenase (LOX) was chosen as a target protein, because this enzyme is known to act at the interface of water and lipid. The effects of addition of boundary lipids on the activity of LOX at the interfaces of emulsion droplets and vesicles were investigated. The activity of LOX was increased dramatically by the addition of PA and fatty acids in vesicle dispersions as well as in emulsions. The kinetic analyses and ζ potential measurements demonstrated that the elevation of LOX activity was due to the increase of adsorptivity of LOX to interfaces through electrostatic interaction. Analyses by dynamic light scattering, electron micrograph and ^<31>P-NMR revealed that the addition of PA and fatty acids induced the formation of hexagonal structure and micellar particles from PC vesicle membranes. These results have shown that "boundary lipids" control the enzymatic activity through modification of membrane structure.