Abstract
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.