脂质氧化诱导的大豆蛋白质聚集机理的研究

利用脂肪氧合酶、亚油酸和大豆分离蛋白构建的模拟体系，研究了脂质氧化诱导的大豆蛋白质聚集的机理。结果表明，在制备大豆分离蛋白的模拟体系中同时添加亚油酸和脂肪氧合酶会使样品的蛋白质氧化值与表面疏水性增加，巯基与二硫键的含量下降，说明脂肪氧合酶催化的脂质氧化可使大豆蛋白结构发生明显的改变。SDS-PAGE电泳表明大豆蛋白7S和11S的各个亚基均参与了反应，尤其是7S部分反应更为明显。HPLC凝胶色谱和激光光散射分析进一步证实反应后的大豆蛋白（RSPI4和5）形成了相对高分子质量和颗粒粒径较大的聚集体。现有的实验证据表明，高度聚集蛋白质的形成可能是通过包括二硫键在内的共价变联，以及诸如氢键、盐桥，尤其是疏水相互作用等的非共价相互作用，形成较大的聚集体。由脂肪氧合酶诱导的蛋白质一脂质相互作用模拟实验的结果说明。脂质氧化对大豆蛋白具有明显的影响；在大豆分离蛋白加工的过程中，控制脂肪氧合酶的活力或脂质的含量是非常重要的。

Mechanism of Aggregation of Soybean Proteins Induced by Lipid Oxidation

A model system consisting of linoleic acid,lipoxygenase and soybean protein isolate was established to investigate the mechanism of aggregation of soybean proteins induced by lipid oxidation.Adding both linoleic acid and lipoxygenase to the reaction system in the preparation of soybean proteins leads to significant increases in protein oxidation and surface hydrophobicity,and decrease of sulfhydryl and disulfide content,reflecting significant change in the structure of reacted soybean proteins(RSP).SDS-PAGE of RSP 4 and 5 shows that subunits of soybean proteins are all involved in the reaction,especially for 7S fractions.SEC-HPLC and laser light scattering indicate that aggregates with high molecular weight and large particle size exist in RSP 4 and 5.The experimental evidences suggest that the aggregates are formed via both non-covalent interactions such as hydrogen bonding,salt bridges and especially hydrophobic interactions,and covalent linkages including disulfide bonds.The formation of protein aggregation induced by the addition of linoleic acid and lipoxygenase suggests that it should be important to control lipoxygenase activity or lipid content during soybean protein isolate processing,and the results of model experiments on protein-lipid interactions catalyzed by lipoxygenase gave efficient evidence for the effect of oxidizing lipid on soybean proteins.