Bläckberg L, Angquist K A, Hernell O
FEBS Lett. 1987 Jun 8;217(1):37-41. doi: 10.1016/0014-5793(87)81237-1.
Human milk contains many enzymes and other biologically active proteins. One of the enzymes, the bile salt-stimulated lipase, constitutes as much as 1% of the milk proteins. Its importance for efficient utilization of milk lipids by the breast-fed infant is now well established. However, whether the lipase protein is a product of protein synthesis within the mammary gland has up till now been an unanswered question. Using biopsy material from lactating human mammary gland we have now demonstrated that the enzyme is synthesized within the gland. This was done by immunoprecipitation of [35S]methionine-labelled protein from tissue pieces. By activity determination we could also determine the amount of enzyme stored in the gland. It was concluded that bile salt-stimulated lipase accounted for 1.3 micrograms/mg tissue protein. Finally, from this figure it could be calculated that about 10-15% of the total protein present in the tissue was milk protein.
人乳含有多种酶和其他生物活性蛋白。其中一种酶，即胆汁盐刺激脂肪酶，占乳蛋白的1%之多。目前已充分证实其对母乳喂养婴儿有效利用乳脂的重要性。然而，脂肪酶蛋白是否为乳腺内蛋白质合成的产物，至今仍是一个未解之谜。我们利用哺乳期人乳腺的活检材料，现已证明该酶是在腺体内合成的。这是通过对组织切片中[35S]甲硫氨酸标记的蛋白质进行免疫沉淀来完成的。通过活性测定，我们还可以确定腺体中储存的酶量。得出的结论是，胆汁盐刺激脂肪酶占组织蛋白的1.3微克/毫克。最后，根据这个数字可以计算出，组织中存在的总蛋白约有10 - 15%是乳蛋白。
