Transglutaminase On Structure Modification And Functional Properties Of Oat Bran Globulin

This research adopts the methods and means of related subjects such as biochemistry, protein chemistry and spectroscopy,etc. Choose oat bran as raw material,adopting alkali-solution and acid-isolation method to extract the oat bran protein. In the presence of glucosamine, using TG to galactosylated modify the oat bran proteins.To analysis the structure, the character of the modifier protein. To point out the important features of the combination of TG and the glucosamine in the oat bran protein. The main research results are as follows:1 To ensure the best extract method of the globulin.The optimal extraction parameters of the globulin is: salt concentration of the extraction is 1.2 mol/L, liquid to solid ratio is 1:16,extraction temperature is 26.5℃, extraction time is 2.0 h, extraction ratio of the globulin is55.87%. Under the optimal conditions, the validation test shows that the extraction ratio of the globulin is 54.84%, which is basically consistent with the theory results. The purity of protein is 83.07%. This provided theoretical basis for the further study of oat bran globulin.2 The glycosylated oat bran globulin with higher grafting degree was produced by the catalysis of TG, in which the single factor design and the response surface methodology(RSM)were used to optimize the grafted condition. The results indicated that the optimal condition by the RSM can be gotten further more on the base of the single factor experiment. On the condition of 0.94:1 for the ratio of amino sugars and globulin concentration, 58 U/g of TG addition, p H7.65, 4 h, and 50℃, the grafting degree of the glycosylated oat bran globulin was 45.6774%,which the value was similar to the predicated one from the model of RSM. This modified protein system with 0.379 mol/kg of the free amino confirmed further that the transglutaminasecatalyzed oat bran globulin present better grafting system than the original one, which indicated a potential further application for the oat bran protein in development of new product.3 Some properties of glycosylated protein have improved compared to the unmodified globulin, such as the solubility, emulsion stability, foaming ability and foam stability. The solubility can reach to 65.83% under the alkaline condition, the emulsion stability increasedabout 38.24% compared to unmodified globulin, the foaming ability increased 25%, the foam stability increased 39.13%; But the surface hydrophobicity has significantly decreased 41%. That is because the glycosyl imported due to the enzymatic of the transgluminase. When the amino sugar connected to the globulin molecules, the spatial molecular structure has changed where the hydroxyl increased. This leads the decline of the hydrophobicity. Additionaly, the denaturation temperature and the enthalpy change value of enzymatic glycosylated protein have declined,where denaturation temperature decreased 5%, enthalpy change value decreased 4%. The transgluinase catalyzes the amino sugar grafted globulin. Although the content of β-folding structure tasks back, its still the vital secondary structure of the glycosylation globulin; Theα-helical structure showed the “up-down” trend and the β-corner structure also showed a decreasing tendency, while the ruleless curly structure barely changed. This demonstrated that glutaminase catalyzed glycosylation globulin has affect on the main chain structure of the secondary structure of protein. The glycosylation of globulin has not effect the corresponding spectrum intensity of tryptophan and tyrosine. The glycosylated globulin tyrosine molecular mainly presents exposure mode. And the relative Raman intensity of tryptophan tends to be embedded. This means that glutaminase catalyzed glycosylation globulin nearly has no affect on the side chain structure of the secondary structure of the protein. The main disulfide vibration mode of the enzymatic glycosylation globulin is t-g-t mode, g-g-t mode has increased significantly, g-g-g vibration mode has decreased. Glycosylation globulin contributes to the formation of the disulfide among the molecules, which promoted the transformation from g-g-g conformation to g-g-t mode. This shows that glutaminase catalyzed glycosylation globulin has affect on the disulfide vibration mode of the protein.