Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546-0215, USA.
Meat Sci. 2012 May;91(1):36-42. doi: 10.1016/j.meatsci.2011.12.002. Epub 2011 Dec 16.
This study investigated the effects of microbial transglutaminase (TG) on structural changes in porcine myofibrillar protein (MP) under varying pH (2.0-6.0) and two ionic strength conditions (0.1M versus 0.6M NaCl). Lowering the pH below the isoelectric point (pI) of myosin induced protein unfolding as revealed by surface hydrophobicity and differential scanning calorimetry. Although the MP solubility at the low ionic strength (0.1M NaCl) was maximal at pH 3.0, both SDS-PAGE profiles and dynamic rheology indicated TG could not cross-link MP under this condition. Based on the carboxyl group content, the TG-catalyzed deamidation was dominant at a pH lower than the pI of myosin (pH 5.0) while cross-linking occurred at higher pH. Moreover, deamidation had no effect on rheological properties of MP. The results indicate that the TG reaction was governed by the pH of substrate protein, and the reaction intensity was related to the solubility of protein.
本研究考察了微生物转谷氨酰胺酶（TG）在不同 pH 值（2.0-6.0）和两种离子强度条件（0.1M 与 0.6M NaCl）下对猪肌原纤维蛋白（MP）结构变化的影响。低于肌球蛋白等电点（pI）会导致蛋白质展开，这可通过表面疏水性和差示扫描量热法来揭示。尽管在低离子强度（0.1M NaCl）下 MP 的溶解度在 pH 3.0 时达到最大值，但 SDS-PAGE 图谱和动态流变学分析表明，在这种条件下 TG 不能使 MP 发生交联。根据羧基含量，在低于肌球蛋白 pI 的 pH 值（pH 5.0）下，TG 催化的脱酰胺作用占主导地位，而在较高的 pH 值下则发生交联。此外，脱酰胺作用对 MP 的流变性质没有影响。结果表明，TG 反应受底物蛋白 pH 值的控制，反应强度与蛋白质的溶解度有关。
