單分子脂質膜在磷脂水解酵素A2水解過程中之組成分析

Analysis of lipid monolayer components during Phospholipase A2 hydrolysis

邱靜儀

指導教授 ： 吳文桂

國立清華大學/電機資訊學院/通訊工程研究所/碩士(2006年)

https://doi.org/10.6843/NTHU.2006.00606

摘要

磷脂水解酵素A2催化水解磷脂質的 sn-2 位置，並且釋放脂肪酸與脫脂酸磷脂質。這些水解產物為重要的二級訊息傅遞者，且與免疫、發炎和生物毒性相關。在本論文中利用霍式轉換紅外線光譜與單分子薄膜技術，來探討在台灣眼鏡蛇毒素中之磷脂水解酵素A2在水解單分子脂質膜時其表面壓力或是表面積的下降之機制。我們發現單分子脂質膜的水解產物脂肪酸離開脂質膜表面是主要造成表面壓力與面積值下降的主因，且脂肪酸離開脂質膜之現象必須在有磷脂水解酵素A2存在下才會發生。此攜帶脂肪酸離開脂質膜的新發現功能，需要在有鈣離子的幫助才能進行。此外，蜜蜂毒素及東非眼鏡蛇蛇毒中之磷脂水解酵素A2也具有此攜帶脂肪酸離開中性脂質膜之功能。而東非眼鏡蛇蛇毒中之磷脂水解酵素A2在水解負電性的脂質膜時，其表面壓力的下降機制似乎是傾向攜帶脫脂酸磷脂質離開脂質膜而非脂肪酸。此不同磷脂水解酵素A2在水解不同電性脂質膜後具攜帶脂肪酸或是脫脂酸磷脂質之特異性，相信可以為磷脂水解酵素A2在毒物、生理及藥理學上之功能多出了一新的研究方向。

關鍵字

磷脂水解酵素A2 ； 血小板活化因子 ； 花生四烯酸 ； 類廿碳酸 ； 前列腺素類

並列摘要

The phospholipase A2 (PLA2) catalyze specially the hydrolysis of the center(sn-2) ester bond of substrate phospholipids. The hydrolysis products of the PLA2 reaction are free fatty acid and lysophospholipid. The fatty acids released by PLA2, such as arachidonic acid (AA) and oleic acid (OA), can be important as stores of energy, but more importantly AA can also function as a second messenger and as the precursor of eicosanoids, which are potent mediators of inflammation and signal transduction.
In this thesis, Fourier transform infrared and Langmuir monolayer are utilized to explore the processes of surface pressure and area decrease of lipid monolayer during PLA2 hydrolysis. Our study showed that PLA2 not only hydrolyzed phospholipid but also carried transported free fatty acid away from membrane interface. The free fatty acid transport phenomenum require calcium ion but is fatty acid chain length independent. Naja nigricolius PLA2 decreased surface area of DMPG monolayer but it cannot transport free fatty acid to the subphase. It implied that Naja nigricolius PLA2 transported Lyso PG instead of free fatty acid chain in negative charge lipid membrane. The aforementioned difference renders new potential research of PLA2 in toxic, physical and pharmacology.

並列關鍵字

Phospholipase A2 ； platelet-activating factor ； arachidonic acid ； eicosanoids ； prostanoids

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