Hydrolysis of milk phospholipid and phospholipid-protein monolayers by pancreatic phospholipase A₂

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• 作者：Sophie Gallier ; Ethan Shaw ; Julia Cuthbert ; Derek Gragson ; Harjinder Singh ; Rafael Jim茅nez-Flores
• 关键词：Phospholipase A2 ; Whey buttermilk phospholipid ; Monolayer ; Hydrolysis ; Liquid-ordered domain
• 刊名：Food Research International
• 出版年：November, 2013
• 年：2013
• 卷：54
• 期：1
• 页码：718-725
• 全文大小：2865 K

文摘

Recently, phospholipids have been used for the liposomal encapsulation of drugs and bioactive compounds. Pancreatic phospholipase A₂ is responsible for the hydrolysis of phospholipids in the intestines. Using fluorescence microscopy, Langmuir monolayers at the air-water interface and atomic force microscopy, the aim of this work was to obtain preliminary data on the effect of the liquid-ordered domains and proteins on the hydrolysis of phospholipids by pancreatic phospholipase A₂. Increasing the enzyme:substrate ratio (1:40 to 1:2) and the temperature (30 掳C to 37 掳C) increased phospholipid hydrolysis as seen by a decrease in surface pressure and change in the surface area corresponding to the formation and desorption of hydrolytic products. Hydrolysis occurred rapidly in the phase coexistence region and led to the clustering of the liquid-ordered domains likely through reduction of electrostatic forces. Atomic force microscopic images of the monolayers under simulated intestinal conditions revealed the presence of packing defects in the liquid-ordered domains where phospholipase A₂ could adsorb. Hydrolysis took place starting in the center of the liquid-ordered domains and proceeded towards their edges. It did not lead to any measurable height changes by atomic force microscopy within the domains but it was evident that mechanical changes took place during hydrolysis. The presence of 尾-casein appeared to increase the rate of hydrolysis, possibly through interaction with phospholipase A₂ at the interface.