Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, 111 Domnească Street, 800201 Galați, Romania.
Biomolecules. 2020 Jul 23;10(8):1096. doi: 10.3390/biom10081096.
In this study, the interaction of native and transglutaminase (Tgase) cross-linked β-lactoglobulin (β-LG) with caffeic acid (CA) was examined, aiming to obtain functional composites. Knowledge on the binding affinity and interaction mechanism was provided by performing fluorescence spectroscopy measurements, after heating the native and cross-linked protein at temperatures ranging from 25 to 95 °C. Regardless of the protein aggregation state, a static quenching mechanism of intrinsic fluorescence of β-LG by CA was established. The decrease of the Stern-Volmer constants with the temperature increase indicating the facile dissociation of the weakly bound complexes. The thermodynamic analysis suggested the existence of multiple contact types, such as Van der Waals' force and hydrogen bonds, between β-LG and CA. Further molecular docking tests indicated the existence of various CA binding sites on the β-LG surface heat-treated at different temperatures. Anyway, regardless of the simulated temperature, the CA-β-LG assemblies appeared to be unstable. Compared to native protein, the CA-β-LG and CA-β-LG complexes (ratio 1:1) exhibited significantly higher antioxidant activity and inhibitory effects on α-glucosidase, α-amylase, and pancreatic lipase, enzymes associated with metabolic syndrome. These findings might help the knowledge-based development of novel food ingredients with valuable biological properties.
在这项研究中，考察了天然和转谷氨酰胺酶（Tgase）交联β-乳球蛋白（β-LG）与咖啡酸（CA）的相互作用，旨在获得功能性复合材料。通过荧光光谱测量，在 25 至 95°C 的温度范围内对天然和交联蛋白进行加热后，提供了关于结合亲和力和相互作用机制的知识。无论蛋白质的聚集状态如何，CA 对β-LG 内源荧光的静态猝灭机制都得以建立。随着温度的升高，Stern-Volmer 常数的降低表明弱结合复合物易于解离。热力学分析表明，β-LG 和 CA 之间存在多种接触类型，如范德华力和氢键。进一步的分子对接测试表明，在不同温度下热处理的β-LG 表面存在各种 CA 结合位点。无论如何，无论模拟温度如何，CA-β-LG 组装体似乎都不稳定。与天然蛋白相比，CA-β-LG 和 CA-β-LG 复合物（比例为 1:1）表现出显著更高的抗氧化活性和对α-葡萄糖苷酶、α-淀粉酶和胰脂肪酶的抑制作用，这些酶与代谢综合征有关。这些发现可能有助于基于知识的新型具有有价值的生物特性的食品成分的开发。
