台灣眼鏡蛇毒中含有三種主要的成份：神經毒素，心臟毒素與磷脂水解酵素A2。其中磷脂水解酵素 A2會水解脂質sn-2的位置而產生脂肪酸鏈與脫脂酸磷脂質，對於細胞膜也有相當的破壞力，因此研究磷脂水解酵素A2與脂質的結合模式與酵素活性的關係是一個相當重要的課題。在本論文中利用霍式轉換紅外線光譜儀與單分子薄膜技術，來研究蜜蜂毒素與台灣眼鏡蛇毒中的兩種磷脂水解酵素A2與脂質在不同的表面壓力下的結合模式及酵素活性的關係，我們以不會被酵素水解的脂質(diether-PC14)所形成的單分子薄膜所進行的實驗發現，磷脂水解酵素A2結合在不同表面壓力下的單分子薄膜時不僅結合的數量隨著壓力的上升而逐漸減少，酵素的截面積也隨著下降。同時利用偏極化霍式轉換紅外線光譜的雙色比值來決定磷脂水解酵素A2與單分子薄膜結合時候的方位，我們發現磷脂水解酵素A2在不同的表面壓力下仍然具有相近的結合角度，也因此可以推論出結合深度隨著脂質表面壓力的上升而變淺。為了了解插入深度與磷脂水解酵素A2活性之關連性，利用DMPC脂質單分子薄膜在加入磷脂水解酵素A2後，我們可以從薄膜上的壓力變化了解單分子薄膜被水解的速率。結果顯示酵素活性在不同薄膜壓力下有一最大值，在台灣眼鏡蛇與蜜蜂毒素的磷脂水解酵素A2分別在壓力18mN/m與24mN/m的時候有其最大的活性，而兩者在活性最大的時候所插入深度皆為2±1Å，表示插入深度很小的時候才會有最大活性。此小的截面積及插入深度才具有最大酵素活性的現象可能是因為在此狀態下的脂質沒有被酵素推開而較易擴散至活性區域，而當壓力太大時磷脂水解酵素A2結合的數量又太少而使總水解活性因此下降。

Abstract
There are three major components of Taiwan Cobra venom: neurotoxin, cardiotoxin and phospholipase A2. Among them, Phospholipase A2 hydrolyzes phospholipids sn-2 position and thus produce fatty acid chain and lysophospholipid. Phospholipase A2 is also destructive to cell membrane. Therefore, it is important to study the binding mode and enzyme activity of phospholipase A2 and lipid. This study focused on binding model and enzyme activity of both bee venom phospholipase A2 and Taiwan cobra phospholipase A2 under different surface pressure by using FTIR-spectrum and monolayer. In the experiment of phospholipase A2 and diether-PC14 monolayer binding, the amount of binding lipid and the area of enzyme cross section both decrease while pressure increases. In addition, the orientation of phospholipase A2 and monolayer binding was determined by polarized FTIR-spectrum dichroic ratio. It was discovered that the orientation of binding was similar under different surface pressure but the penetration depth will decrease while surface pressure increases. DMPC monolayer was used to understand the relationship between enzyme activity and penetration. The pressure alteration shows the hydrolyzed rate of monolayer. The result showed that there was a maximum enzyme activity under different surface pressure. The enzyme activities of Taiwan Cobra venom and bee venom will reach the maximum when pressure is 18mN/m and 24mN/m separately. In the meantime, penetration of both enzymes is 2±1Å. This shows that there will be maximum enzyme activity only when penetration is peripheral. It was suggested that when penetration is peripheral, lipid might not be excluded by enzyme so lipid might diffuse to active site easily. Hence, when pressure is high and phospholipase A2 and monolayer binding is little, enzyme activity will decrease.

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