谷朊的糖基化及其谷氨酰胺转氨酶脱酰胺改性研究

Study on Deamidated Modification of Maillard Conjugated Wheat Gluten with Carbohydrates by Microbial Transglutaminase

谷朊富含谷氨酰胺和较多的疏水性氨基酸,具有不溶于水等独特性质。试验采用糖基化和谷氨酰胺转氨酶对谷朊改性,使蛋白质分子带有更多的极性基团,从而使其功能性质得到改善。研究首先在60℃,75%的相对湿度下对谷朊进行糖基化,当谷朊与葡萄糖和葡聚糖的质量比均为10∶1,Maillard反应时间24h,糖基化后的谷朊可利用的ε-NH2分别下降了40%和20%左右。2种糖基化谷朊在底物浓度为5%,谷氨酰胺转氨酶(MTG)浓度为100 U/g谷朊,在pH 6.0,37℃条件下进行脱酰胺改性,MTG作用7 h后,葡萄糖和葡聚糖糖基化谷朊氨释放量分别达到40μM氨/g蛋白和50μM氨/g蛋白,高于非糖基化谷朊的31μM氨/g蛋白,经MTG改性后的糖基化谷朊表面疏水性和溶解性有小幅度的提高,但持水性和持油性有较大提高。

Wheat gluten is rich with glutamine and hydrophobic amino acids, and has some unique properties such as poor water-solubility, etc. To improve its functional properties gluten was modified by glycosylation followed by microbial transglutaminase （MTGase） deamidation with increasing polar groups on gluten. In this study, firstly, wheat gluten was incubated 24 hours with glucose or dextran at 60℃ and 75% relative humidity to promote the formation of Maillard reaction. Available ε-NH2 groups Of wheat gluten were masked approximately 40% and 20% respectively. A 5% suspension solution of glycosylated glutens was to he deamidated by MTGase 100 U/g gluten at 37℃ , pH 6.0 for 7 h, the amount of NH3 released during the reaction reached 40 μM NH3/g protein and 50μM NH3/g protein while the amount of NH3 released reached 31μM NHa/g protein to un-glyeosylated glutens. After gluten was glycosylated followed by MTGase reaction, the surface hydrophobicity and the solubility property were slightly increased. The water holding capacity and oil holding capacity were raised effectively by deamidation.