Moreno F Javier, Mackie Alan R, Mills E N Clare
Institute of Food Research, Norwich Research Park, Colney Lane, Norwich NR4 7UA, United Kingdom.
J Agric Food Chem. 2005 Dec 14;53(25):9810-6. doi: 10.1021/jf0515227.
Interactions with food components may alter the resistance of food proteins to digestion, a property thought to play an important role in determining allergenic properties. The kinetics of breakdown of the bovine milk allergen alpha-lactalbumin during in vitro gastrointestinal digestion was found to be altered by interactions with physiologically relevant levels of phosphatidylcholine (PC), a surfactant that is abundant both in milk and is actively secreted by the stomach. Breakdown during gastric digestion was slowed in the presence of PC and accompanied by small alterations in the profile of resulting peptides, with little effect being observed during subsequent duodenal digestion. alpha-Lactalbumin was found to unfold at gastric (acid) pH, giving a CD spectrum similar to that obtained for the partially folded state it is known to adopt at pH values below its isoelectric point. Fluorescence polarization studies performed at low pH indicated that this partially unfolded form of the protein was able to penetrate into the PC vesicles. These interactions are probably responsible for the slowing of gastric digestion by reducing the accessibility of the protein to pepsin. These findings show that interactions with other food components, such as lipids, may alter the rate of breakdown of food proteins in the gastrointestinal tract. It underlines the importance of the food matrix in affecting patterns of food allergen digestion and hence presentation to the immune system and that in vitro digestion systems used for assessing digestibility of allergens must take account of surfactants.
与食物成分的相互作用可能会改变食物蛋白质对消化的抗性，这一特性被认为在决定过敏原特性方面起着重要作用。研究发现，在体外胃肠道消化过程中，牛乳过敏原α-乳白蛋白的分解动力学因与生理相关水平的磷脂酰胆碱（PC）相互作用而改变，PC是一种在牛奶中含量丰富且由胃主动分泌的表面活性剂。在有PC存在的情况下，胃消化过程中的分解速度减慢，同时产生的肽谱有微小变化，而在随后的十二指肠消化过程中几乎没有观察到影响。研究发现α-乳白蛋白在胃（酸性）pH值下会展开，其圆二色光谱与在低于其等电点的pH值下已知采用的部分折叠状态所获得的光谱相似。在低pH值下进行的荧光偏振研究表明，这种蛋白质的部分未折叠形式能够穿透到PC囊泡中。这些相互作用可能是通过降低蛋白质对胃蛋白酶的可及性而导致胃消化减慢的原因。这些发现表明，与其他食物成分（如脂质）的相互作用可能会改变胃肠道中食物蛋白质的分解速度。这凸显了食物基质在影响食物过敏原消化模式以及进而影响向免疫系统呈递方面的重要性，并且用于评估过敏原消化性的体外消化系统必须考虑表面活性剂。
