转谷氨酰胺酶交联大豆分离蛋白结构表征

为研究转谷氨酰胺酶（transglutaminase，TGase）交联大豆分离蛋白（soy protein isolate，SPI）对SPI分子结构的影响，采用差示扫描量热仪、扫描电镜、X-射线衍射、红外光谱、圆二色谱等对TGase交联SPI前后二级结构的变化进行分析。结果表明：交联后SPI表面疏水性增强，自由氨基含量降低，结构和微观晶体结构均发生变化，结构由球形结构变成凹陷孔状，多肽链充分伸展，空间结构改变，结晶度降低；β-折叠含量升高，有序度更高，无规卷曲结构含量相对较低；利用氨基酸全自动分析仪测定氨基酸含量，交联后必需氨基酸含量提高了5.5%，疏水性氨基酸含量提高了14.5%，表明交联后提高了SPI营养价值，改善SPI的表面疏水性。

Structural Characterization of Translutaminase Cross-linked Soy Protein Isolate

This study aimed to examine the effect of translutaminase (TGase) cross-linking on the molecular structure of soybean protein isolate (SPI). The structural changes of SPI before and after cross linking were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy, X-ray, infrared spectroscopy and circular dichroism spectroscopy. The results showed that after being cross-linked, the surface hydrophobicity of SPI increased, and the content of free amino groups reduced. The structure and microcrystal structure changed from spherical to concave, with the polypeptide chains stretched adequately, the spatial structure changed and the crystallinity decreased; the β-fold content increased, the structure becoming more ordered, while the random coil content decreased. Finally, we found that the content of essential amino acids increased by 5.5% and the content of hydrophobic amino acids by 14.5%, indicating that the nutritional value and surface hydrophobicity of SPI was improved after cross linking, as analyzed by an amino acid automatic analyzer.