Kim H H, Jimenez-Flores R
Department of Food Science, University of Illinois, Urbana 61801.
J Dairy Sci. 1994 Aug;77(8):2177-90. doi: 10.3168/jds.S0022-0302(94)77160-5.
The major proteins in milks from bovine, caprine, porcine, and murine animals and from humans were compared using a two-dimensional analysis method. In the first dimension, proteins were separated by their isoelectric points using preparative isoelectric focusing in pH gradient of 3 to 10. Twenty fractions from each sample were then analyzed by urea-PAGE and SDS-PAGE. Two-dimensional gels showed characteristic patterns for each milk. Major bovine milk proteins were identified and used as reference for proteins of other mammals. Additionally, some peptides resulting from plasmin hydrolysis were characterized. Caprine milk proteins showed a pattern similar to that of bovine milk except for the absence of alpha s1-caseins. alpha-Lactalbumin of bovine and caprine milks resolved as two bands in an immunoblot using bovine alpha-lactalbumin antibody. Each band corresponded to normal and glycosylated alpha-lactalbumin. Human, porcine, and murine milk proteins were totally different from those of ruminant milks on the two-dimensional gels. Two-dimensional analysis using preparative isoelectric focusing, followed by PAGE, was a useful method to compare major milk proteins in several mammals because of the rapid simultaneous separation into 20 fractions. This fractionation allows additional analytical procedures for more efficient comparison of chemical and physical properties of the proteins.
采用二维分析方法对牛、羊、猪、鼠以及人类乳汁中的主要蛋白质进行了比较。在第一维中，利用pH值为3至10的梯度制备性等电聚焦，根据等电点对蛋白质进行分离。然后，对每个样品的20个组分进行尿素聚丙烯酰胺凝胶电泳（urea-PAGE）和十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）分析。二维凝胶显示了每种乳汁的特征图谱。确定了主要的牛乳蛋白，并将其用作其他哺乳动物蛋白质的参照。此外，还对纤溶酶水解产生的一些肽进行了表征。除了缺乏αs1-酪蛋白外，羊乳蛋白的图谱与牛乳蛋白相似。在使用牛α-乳白蛋白抗体的免疫印迹中，牛和羊乳中的α-乳白蛋白分离为两条带。每条带分别对应正常的和糖基化的α-乳白蛋白。在二维凝胶上，人乳、猪乳和鼠乳蛋白与反刍动物乳汁中的蛋白完全不同。由于能快速同时分离成20个组分，采用制备性等电聚焦后进行聚丙烯酰胺凝胶电泳的二维分析方法，是比较几种哺乳动物主要乳蛋白的一种有用方法。这种分级分离允许进行额外的分析程序，以便更有效地比较蛋白质的化学和物理性质。
