Structure of thaumatin under acidic conditions: Structural insight into the conformations in lysine residues responsible for maintaining the sweetness after heat-treatment
Structure of thaumatin under acidic conditions: Structural insight into the conformations in lysine residues responsible for maintaining the sweetness after heat-treatment
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酸性条件下索马甜的结构：对赖氨酸残基中负责在热处理后保持甜味的构象的结构了解
DOI：
10.1016/j.foodchem.2022.132996
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发表时间：
2022
期刊：
影响因子：
8.8
通讯作者：
Mikami Bunzo
中科院分区：
文献类型：
--
作者：
Masuda Tetsuya;Okubo Kyohei;Baba Seiki;Suzuki Mamoru;Tani Fumito;Yamasaki Masayuki;Mikami Bunzo
它是一种非常甜的蛋白质。它的甜味在酸性条件下加热时仍然存在，但在pH值超过7.0时加热就会消失。为了阐明在酸性条件下加热时，thumatin的结构特征是如何抵抗不溶性聚集的，我们分析了在pH 4.0、6.0和8.0下获得的thumatin晶体结构。同时，用差示扫描荧光法测定了这些pH值下的熔化温度（Tm）。pH 4.0时，其结构的tof值明显低于pH 6.0时，其结构的总体b因子值高于pH 6.0时。有趣的是，大多数赖氨酸残基的相对b因子值随着pH值的降低而降低。这些结果表明，在pH 4.0时，整体结构变得柔韧，但某些区域的相对柔韧度低于pH 6.0时。因此，相对柔韧性的降低可能在防止热聚集方面发挥重要作用，从而保持甜度。
Thaumatin is an intensely sweet-tasting protein. Its sweetness persists when heated under acidic conditions, but disappears when heated at a pH above 7.0. To clarify how the structural features of thaumatin resist insoluble aggregation during heating under acidic conditions, we analysed its crystal structure obtained at pH 4.0, 6.0, and 8.0. Simultaneously, the melting temperature (Tm) at these pH levels was determined using differential scanning fluorimetry. At pH 4.0, theTmof thaumatin was substantially lower and the overallB-factor value of its structure was higher than those at pH 6.0. Interestingly, the relativeB-factor values for most lysine residues decreased as the pH reduced. These results suggest that the overall structure at pH 4.0 becomes flexible but the relative flexibility of some regions is lower than that at pH 6.0. Thus, the reduction in relative flexibility might play an important role in preventing thermal aggregation, thereby maintaining the sweetness.