糖链长度对于大豆7S球蛋白糖基化产物构象及乳化特性的影响

Effect of Chain Length of Dextrans on the Conformation and Emulsifying Properties of the Glycosylation Products of Soybean 7S Globulin

摘要:

本文研究了3种糖链长度的葡聚糖和大豆7S球蛋白的糖基化产物，分析糖链长度对Maillard反应程度、产物构象和产物乳化性方面的影响机制，研究显示，分子量在67~150 u范围的葡聚糖反应程度明显高于分子量为500 u葡聚糖和蛋白质的糖基化反应；以共价键形式结合入蛋白质肽链的葡聚糖，不会改变大豆7S球蛋白二级结构的主要结构（β-结构），主要增加了蛋白质二级结构中的无规则卷曲结构，三级结构中，随着糖链的延长，较大程度地屏蔽掉近紫外区有信号的芳香族氨基酸圆二信号，尤其是苯丙氨酸特征信号逐渐减少；随着糖链的延长，糖基化产物的空间位阻效应增加，乳化性逐渐提高，分子量为500 u葡聚糖链长与另外两种相差比较大。

Abstract:

The dextrans with varied chain lengths and the glycosylation products of soybean 7S globulin were studied in this paper. Further, the mechanisms underlying the impact of dextran chain length on the extent of Maillard reaction and the conformation and emulsifying properties of the glycosylation products were analyzed. The study showed that the extent of protein glycosylation reaction achieved using dextran with a molecular weight of 67~150 u was significantly higher than those with a molecular weight of 500 u. The glucan moiety that is covalently linked to the protein peptide did not change the major conformation of the secondary structure (β-structure) of soybean 7S globulin, rather it mainly increased the random coil in the secondary structure of the protein. In case of the tertiary structure, with increasing length of sugar chains, the circular dichroism (CD) spectral signals of the aromatic amino acids near ultraviolet (UV) region were significantly blocked, particularly for phenylalanine whose characteristic signals were gradually reduced. Moreover, with increasing lengths of the sugar chain, the steric hindrance effect of the glycosylation products increased, and the emulsifying properties were gradually enhanced. However, the chain length of 500 u glucan showed a significant difference compared to the other two chain lengths.