Perez M D, Sanchez L, Aranda P, Ena J M, Oria R, Calvo M
Tecnología y Bioquímica de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Spain.
Biochim Biophys Acta. 1992 Jan 24;1123(2):151-5. doi: 10.1016/0005-2760(92)90105-5.
The interaction of bovine beta-lactoglobulin with palmitic and oleic acids has been studied by a partition equilibrium method. Bovine beta-lactoglobulin displays only one high affinity binding site for fatty acids whose association constants for palmitic and oleic acids are 4.2 x 10(6) and 2.3 x 10(6) M-1, respectively. However, other binding sites with low affinity are also present. The existence of one high affinity binding site is in accordance with the amount of fatty acids naturally bound to beta-lactoglobulin isolated from milk. The effect of beta-lactoglobulin on ruminant pregastric lipases from a pharyngeal extract has been assayed. The activity of pharyngeal lipase on a triglyceride emulsion is increased about 200%, 250% and 190% in the presence of 10 mg/ml, 20 mg/ml and 40 mg/ml of beta-lactoglobulin, respectively, the last concentration representing that found physiologically in colostrum. Albumin, another ligand-binding protein, increases the activity of this enzyme to a lesser extent and high levels tend to inhibit enzyme action. These results indicate that beta-lactoglobulin could participate in the digestion of milk lipids during the neonatal period by enhancing the activity of pregastric lipase through removal of the fatty acids that inhibit this enzyme.
采用分配平衡法研究了牛β-乳球蛋白与棕榈酸和油酸的相互作用。牛β-乳球蛋白对脂肪酸仅显示一个高亲和力结合位点，其对棕榈酸和油酸的缔合常数分别为4.2×10⁶和2.3×10⁶ M⁻¹。然而，也存在其他低亲和力的结合位点。一个高亲和力结合位点的存在与从牛奶中分离出的天然结合脂肪酸的β-乳球蛋白的量一致。测定了β-乳球蛋白对来自咽提取物的反刍动物前胃脂肪酶的影响。在分别存在10 mg/ml、20 mg/ml和40 mg/ml的β-乳球蛋白时，咽脂肪酶对甘油三酯乳液的活性分别提高了约200%、250%和190%，最后一个浓度代表初乳中生理上发现的浓度。白蛋白是另一种配体结合蛋白，其对该酶活性的提高程度较小，且高浓度往往会抑制酶的作用。这些结果表明，β-乳球蛋白可能通过去除抑制该酶的脂肪酸来增强前胃脂肪酶的活性，从而参与新生儿期乳脂的消化。
