Yoneda M, Shiraishi J, Kuraishi T, Aoki F, Imakawa K, Sakai S
Department of Animal Breeding, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Japan.
J Dairy Sci. 2001 Aug;84(8):1851-5. doi: 10.3168/jds.S0022-0302(01)74625-5.
Casein micelles of mouse milk consist of alpha-, beta-, gamma-, and kappa-caseins. By digestion with alkaline phosphatase, they were separated as an independent band by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). The compositions of alpha-, beta-, gamma-, and kappa-caseins were 24.3, 25.1, 9.4, and 41.2% in colostrum, and 36.8, 15.6, 11.9, and 35.7% in mature milk, respectively. Zero-day-old pups were allowed to access either colostrum or mature milk, and the aggregated milk in the stomach was analyzed by SDS-PAGE. Caseins in colostrum were digested more rapidly and efficiently than those in mature milk. Among the seven peptides present in the aggregated caseins, four peptides were colostrum-specific and derived from alpha- and gamma-caseins. It was expected that colostrum-specific and soluble peptides were generated from alpha- and gamma-caseins through gastric proteinase digestion. Amino acid sequence analysis and the pH of the aggregated milk suggested that caseins in the stomach were digested by a chymotrypsin-like proteinase. Caseins in colostrum were different from those in mature milk, with respects to the casein composition as well as the gastric proteinase sensitivity. It is concluded that the lactating mice on the day of parturition supply particular caseins to their young.
小鼠乳中的酪蛋白胶粒由α-、β-、γ-和κ-酪蛋白组成。经碱性磷酸酶消化后，通过十二烷基硫酸钠（SDS）-聚丙烯酰胺凝胶电泳（PAGE）将它们分离成一条独立的条带。初乳中α-、β-、γ-和κ-酪蛋白的组成分别为24.3%、25.1%、9.4%和41.2%，成熟乳中分别为36.8%、15.6%、11.9%和35.7%。让出生0天的幼崽获取初乳或成熟乳，并通过SDS-PAGE分析胃中的聚集乳。初乳中的酪蛋白比成熟乳中的酪蛋白消化得更快、更有效。在聚集的酪蛋白中存在的七种肽中，四种肽是初乳特异性的，来源于α-和γ-酪蛋白。预计通过胃蛋白酶消化，α-和γ-酪蛋白会产生初乳特异性的可溶性肽。氨基酸序列分析和聚集乳的pH值表明，胃中的酪蛋白被一种类胰凝乳蛋白酶消化。初乳中的酪蛋白在酪蛋白组成以及对胃蛋白酶的敏感性方面与成熟乳中的酪蛋白不同。得出的结论是，分娩当天的泌乳小鼠会向幼崽提供特殊的酪蛋白。
