Sun Yuanxia, Hayakawa Shigeru, Izumori Ken
Department of Biochemistry and Food Science, Kagawa University, Ikenobe, Miki, Kagawa 761-0795, Japan.
J Agric Food Chem. 2004 Mar 10;52(5):1293-9. doi: 10.1021/jf030428s.
The effect of nonenzymatic glycation on the structural changes and gelling properties of hen ovalbumin (OVA) through the Maillard reaction was studied. OVA was incubated at the dry state with a rare ketohexose (D-psicose, Psi) and two alimentary sugars (D-fructose, Fru; D-glucose, Glc) at 55 degrees C and 65% relative humidity. To evaluate the modification of OVA by different reducing sugars during the glycation process, the extent of the Maillard reaction, aggregation processes, structural changes, and gelling behaviors were investigated. Reactivity of Psi with the protein amino groups was much lower than that of both Fru and Glc, whereas Psi induced production of browning and fluorescent substances more strongly than the two alimentary sugars did. Furthermore, OVA showed an increased tendency toward multimeric aggregation upon modifying with Psi through covalent bond. The modified OVAs with reducing sugar were similar to nonglycated control sample in Fourier transform infrared (FT-IR) characteristics, but significantly decreased in intensity of tryptophan-related fluorescence. The results indicate that although glycation brought about similar changes in the secondary structure without great disruption of native structure, its influence on the side chains of protein in tertiary structure could be different. Breaking strength of heat-induced glycated OVA gels with Psi was markedly enhanced by the Maillard reaction. These results suggest that Psi had a strong cross-linking activity with OVA; consequently, the glycated OVA with Psi could improve gelling properties under certain controlled conditions.
研究了通过美拉德反应，非酶糖基化对鸡卵清蛋白（OVA）结构变化和凝胶特性的影响。将OVA在干燥状态下与一种稀有己酮糖（D-阿洛酮糖，Psi）以及两种食用糖（D-果糖，Fru；D-葡萄糖，Glc）在55℃和65%相对湿度下孵育。为了评估糖基化过程中不同还原糖对OVA的修饰作用，研究了美拉德反应程度、聚集过程、结构变化和凝胶行为。Psi与蛋白质氨基的反应性远低于Fru和Glc两者，但Psi比两种食用糖更强烈地诱导了褐变和荧光物质的产生。此外，通过共价键用Psi修饰后，OVA呈现出多聚体聚集增加的趋势。用还原糖修饰的OVA在傅里叶变换红外（FT-IR）特征方面与未糖基化的对照样品相似，但色氨酸相关荧光强度显著降低。结果表明，虽然糖基化在二级结构上带来了相似的变化，而未对天然结构造成很大破坏，但其对三级结构中蛋白质侧链的影响可能不同。美拉德反应显著增强了用Psi热诱导糖基化的OVA凝胶的断裂强度。这些结果表明，Psi与OVA具有很强的交联活性；因此，在某些可控条件下，用Psi糖基化的OVA可以改善凝胶特性。
