Hurley W L, Grieve R C, Magura C E, Hegarty H M, Zou S
Department of Animal Sciences, University of Illinois, Urbana 61801.
J Dairy Sci. 1993 Feb;76(2):377-87. doi: 10.3168/jds.S0022-0302(93)77356-7.
Lactoferrin and Ig are the major glycosylated proteins in whey preparations from colostrum, milk, nonlactating bovine mammary secretions, and milk collected after intramammary endotoxin challenge. Lactoferrin was isolated from these sources and from bovine mammary tissue (nonlactating) and bovine milk neutrophils. Molecular weight forms of isolated lactoferrins were separated by SDS-PAGE. Apparent molecular weight forms of lactoferrin (approximately 83 and 87 kDa) did not differ among lactoferrins isolated from mammary secretions or from mammary tissue, but lactoferrin isolated from milk neutrophils migrated as different molecular weight bands in the gels (approximately 87 and 91 kDa). Human milk lactoferrin also separated as two distinct bands in the gels. All forms of lactoferrin were glycosylated. Differences were distinct in the glycosylation pattern of lactoferrins from human milk, bovine nonlactating mammary secretion, and bovine milk neutrophils. Enzymatic deglycosylation of lactoferrins from those sources resulted in migration of each as a single band (approximately 77 kDa). Apparent molecular weight forms of lactoferrin observed by separation by SDS-PAGE are not the result of genetic variance or differential glycosylation at different stages of mammary gland function. Nevertheless, the forms of lactoferrin result from the presence of glycans on the protein.
乳铁蛋白和免疫球蛋白是初乳、牛奶、非泌乳期奶牛乳腺分泌物以及乳腺内毒素攻击后采集的牛奶中乳清制剂中的主要糖基化蛋白。乳铁蛋白从这些来源以及奶牛乳腺组织（非泌乳期）和牛奶中性粒细胞中分离得到。通过SDS-PAGE分离所得到的乳铁蛋白的分子量形式。从乳腺分泌物或乳腺组织中分离得到的乳铁蛋白的表观分子量形式（约83和87 kDa）并无差异，但从牛奶中性粒细胞中分离得到的乳铁蛋白在凝胶中迁移为不同分子量条带（约87和91 kDa）。人乳铁蛋白在凝胶中也分离为两条不同的条带。所有形式的乳铁蛋白均被糖基化。来自人乳、奶牛非泌乳期乳腺分泌物和牛奶中性粒细胞的乳铁蛋白的糖基化模式存在明显差异。对来自这些来源的乳铁蛋白进行酶促去糖基化处理后，每种乳铁蛋白均迁移为单一一条带（约77 kDa）。通过SDS-PAGE分离观察到的乳铁蛋白的表观分子量形式并非乳腺功能不同阶段的遗传变异或差异糖基化的结果。然而，乳铁蛋白的这些形式是由于蛋白质上存在聚糖所致。
