Potential host-defense role of a human milk vitamin B-12-binding protein, haptocorrin, in the gastrointestinal tract of breastfed infants, as assessed with porcine haptocorrin in vitro
Potential host-defense role of a human milk vitamin B-12-binding protein, haptocorrin, in the gastrointestinal tract of breastfed infants, as assessed with porcine haptocorrin in vitro
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DOI：
10.1093/ajcn/77.5.1234
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发表时间：
2003-05-01
影响因子：
7.1
通讯作者：
Lönnerdal, B
中科院分区：
文献类型：
--
作者：
Adkins, Y;Lönnerdal, B
背景：关于母乳中维生素B-12结合蛋白--触角蛋白的生物学作用的信息有限。人乳腺上皮细胞表达结合角蛋白及其在母乳中的存在提示母乳喂养婴儿具有潜在的生理功能。目的：研究在体外模拟母乳喂养婴儿胃肠道的条件下，结合角蛋白对蛋白质降解和抗菌活性的影响。设计：建立一种模拟婴儿胃肠消化的体外模型。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法、Western印迹分析、柱层析、基质辅助激光解吸电离飞行时间质谱仪(MALDI-TOF MS)等方法研究了猪血清白蛋白在消化酶(胃酶和胰酶)作用下的结构稳定性。通过与致病性大肠杆菌O127菌株2348/69孵育和细菌生长监测，测定了结合角蛋白的抗菌活性。结果：酶作用下的结合角蛋白的结构分析没有发现其相对分子质量下降，说明结合角蛋白能抵抗蛋白质的降解。接触消化酶的触角蛋白和未消化的触角蛋白都能抑制致肠性大肠杆菌的生长，其作用程度相似。因此，在体外，结合角蛋白不仅保留了其在蛋白酶作用下的结构，而且具有一定的抗菌活性。结论：在母乳喂养的婴儿的胃肠道中，结合角蛋白可能具有抗病原体的宿主防御功能。
Background: Limited information exists on the biological role of a vitamin B-12-binding protein, haptocorrin, in human milk. The expression of haptocorrin by human mammary epithelial cells and its presence in human milk suggest a potential physiologic function in breastfed infants.Objective: We investigated the extent to which haptocorrin could withstand proteolytic degradation and exert antimicrobial activity under in vitro conditions designed to simulate the gastrointestinal tract of breastfed infants.Design: An in vitro model that simulates infant gastric and intestinal digestion was developed. The structural stability of porcine haptocorrin after exposure to digestive enzymes (pepsin and pancreatin) was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot analysis, column chromatography, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The antimicrobial activity of haptocorrin was determined by incubating haptocorrin with enteropathogenic Escherichia coli O127 strain 2348/69 and monitoring bacterial growth.Results: The structural analysis of haptocorrin exposed to enzymes did not show a decrease in molecular weight, which indicated that haptocorrin can survive proteolytic degradation. Both haptocorrin exposed to digestive enzymes and undigested haptocorrin inhibited the growth of enteropathogenic E. coli and did so to a similar extent. Thus, haptocorrin in vitro not only retains its structure after exposure to proteases but also exhibits antimicrobial activity.Conclusion: These results suggest that haptocorrin may exert a host-defense function against pathogens in the gastrointestinal tracts of breastfed infants.