燕麦麸皮球蛋白的糖基化结构修饰及功能性变化

在氨基葡萄糖存在的条件下,利用转谷氨酰胺酶(transglutaminase,TG)对燕麦麸皮球蛋白糖基化结构修饰,进而探讨糖基化蛋白功能性质与结构之间的关系。结果表明,糖基化交联球蛋白的溶解性、乳化稳定性、起泡性及泡沫稳定性相比于未修饰的球蛋白都有明显的改善,但表面疏水性明显下降;另外,酶促糖基化球蛋白的变性温度和焓变值都有所下降,其二级结构变化为:α-螺旋结构相对含量呈增加趋势,β-折叠和β-转角结构相对含量呈下降趋势,无规卷曲结构相对含量几乎没变。经糖基化处理的球蛋白酪氨酸分子主要呈现"暴露态",色氨酸相对拉曼强度更趋近于"包埋态"。酶促糖基化球蛋白二硫键振动模式为t-g-t。通过对球蛋白、修饰球蛋白的功能特性与空间构象的比较分析,明确TG催化葡萄糖结合在燕麦麸球蛋白上,进一步明晰修饰蛋白功能特性与空间构象之间的构效关系。结果可为延长杂粮产业链提供良好的理论依据,同时可以为今后制备燕麦蛋白特定产品进行分子设计和重组提供基础数据。

Structural Modification of Oat Bran Globulin by Glycosylation and Change in Its Functional Properties

In the presence of glucosamine, oat bran globulin was subjected to glycosylation using transglutaminase (TG) for analyzing and correlating the structural and functional characteristics of the modified protein. The results showed that some properties of the glycosylated protein were improved when compared to the unmodified one, such as solubility, emulsion stability, foaming ability and foam stability. However, the surface hydrophobicity was significantly decreased. Additionally, the denaturation temperature and enthalpy change of the protein declined after glycosylation. The secondary structure contents changed, as indicated by an increase in α-helix, a decrease in β-sheet and β-turn and almost no change in random coil. The tyrosine residues of the glycosylated globulin were exposed, whereas the tryptophan residues were buried. Moreover, the disulfide stretching vibration mode was t-g-t. A comparison of functional properties and spatial conformation between the modified and unmodified globulin demonstrated that TG catalyzed the binding of glucose to oat bran globulin, further confirming the relationship between its functional characteristics and spatial conformation. The findings of this study may provide a theoretical basis for extending the minor grain industry chain, and offer basic data to study molecular design and intermolecular recombination for the production of special products based on oat bran protein.