Antioxidant nature of bovine milk β-lactoglobulin
Antioxidant nature of bovine milk β-lactoglobulin
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DOI：
10.3168/jds.s0022-0302(07)71538-2
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发表时间：
2007-02-01
影响因子：
3.5
通讯作者：
Mao, S. J. T.
中科院分区：
文献类型：
--
作者：
Liu, H. C.;Chen, W. L.;Mao, S. J. T.
乳制品行业加工牛奶时需要加热，这显然会导致 β-乳球蛋白 (β-LG) 的构象发生变化。 β-乳球蛋白是一种主要蛋白质，约占乳蛋白总量的 10% 至 15%，是一种由 162 个 AA 组成的球状蛋白质，相对分子质量为 18.4 kDa。本研究的目的是确定牛奶中 β-LG 的抗氧化作用及其可能的机制。我们证明，β-LG 是一种温和的抗氧化剂，其效力低于维生素 E 和普罗布考（后者是用于临床治疗的抗氧化剂）。 β-LG单体向二聚体的转化在一定程度上决定了保护低密度脂蛋白免受铜诱导氧化的作用模式。通过加热（100℃，2分钟）交联β-LG的游离硫醇基团，或通过羧甲基化对β-LG进行化学修饰以封闭硫醇基团，导致抗氧化活性显着损失。数据表明 Cys-121 在 β-LG 的抗氧化性质中发挥着重要作用。通过使用抗 LG 抗体亲和柱消耗牛奶中的 β-LG，我们从损失的抗氧化活性中观察到，β-LG 贡献了大约 50% 的总活性。由于β-LG对热变性极为敏感，为了保持其抗氧化性质，日常食用的乳制品不宜过热，以保持其抗氧化性质。
Heating is necessary for processing milk in the dairy industry, which evidently produces a conformational change in beta-lactoglobulin (beta-LG). beta-Lactoglobulin, a major protein that accounts for approximately 10 to 15% of total milk proteins, is a globular protein consisting of 162 AA with a relative molecular mass of 18.4 kDa. The purpose of the present study was to determine the antioxidant role of beta-LG in milk and the possible mechanism involved. We showed that beta-LG is a mild antioxidant whose potency is less than that of vitamin E and probucol (the latter being an antioxidant used for clinical therapy). The conversion of the beta-LG monomer to dimer was responsible, in part, for the mode of action in protecting low- density lipoproteins against copper-induced oxidation. Cross-linking the free thiol groups of beta-LG by heating (100 degrees C for 2 min), or chemically modifying the beta-LG by carboxymethylation to block the thiol groups resulted in a substantial loss of antioxidant activity. The data suggest that Cys-121 plays an essential role in the antioxidant nature of beta-LG. By using an anti-LG antibody affinity column to deplete the beta-LG from milk, we observed from the lost antioxidant activity that beta-LG contributes approximately 50% of the total activity. Because beta-LG is extremely sensitive to thermal denaturation, to maintain its antioxidant nature, dairy products consumed daily should not be overheated in order to maintain its antioxidant nature.