Effect of pH shifting on conformation and gelation properties of myosin from skeletal muscle of blue round scads(Decapterus maruadsi)
Effect of pH shifting on conformation and gelation properties of myosin from skeletal muscle of blue round scads(Decapterus maruadsi)
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pH值变化对蓝圆鱼(Decapterus maruadsi)骨骼肌肌球蛋白构象和凝胶特性的影响
DOI：
10.1016/j.foodhyd.2019.02.026
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发表时间：
2019
影响因子：
10.7
通讯作者：
Cao Min-Jie
中科院分区：
文献类型：
--
作者：
Sun Le-Chang;Lin Yi-Chen;Liu Wei-Feng;Qiu Xu-Jian;Cao Kai-Yuan;Liu Guang-Ming;Cao Min-Jie
为了阐明等电增溶/沉淀法回收的蓝色圆球分离蛋白的凝胶形成机理，研究了酸性(AM)和碱性(KM)pH漂移处理的主要蛋白质肌球蛋白的物理化学、构象和凝胶性质，并与天然肌球蛋白(NM)进行了比较。在40 °C时，所有肌球蛋白样品的溶解度显著下降，颗粒大小、浊度和表面疏水性显著增加。在样品中，当温度高于40 °C时，AM的溶解度最低，浊度最高，比NM和KM高，表明AM更容易变性和团聚。圆二色谱(CD)分析表明，酸性和碱性pH处理都导致了肌球蛋白构象的变化，以及α-螺旋含量的变化。当pH重新调整到中性时，KM恢复了与NM相似的结构，而AM未能重新折叠到其自然状态。NM在90 °C时表现出最高的储能模量(G‘)，而AM则表现出最低的G’值。此外，AM在加热过程中没有明显变化，特别是在凝胶温度范围(60-90 °C)。这些结果强烈表明，酸处理导致肌球蛋白不可逆的构象变化，从而在加热的初始阶段导致剧烈的变性和聚集，最终导致凝胶形成能力的完全丧失。从另一方面来说，碱性pH移动法更适合于从蓝色圆盘中回收蛋白质。
To clarify the gel formation mechanism of isolated proteins recovered from blue round scads by isoelectric solubilization/precipitation, the physiochemical, conformational and gelation properties of the major protein myosin treated by acidic-(AM) or alkaline-(KM) pH-shifting were investigated and compared with native myosin (NM). The solubility in all myosin samples dropped significantly at 40 °C, with remarkable increases of particle size, turbidity and surface hydrophobicity. Among the samples, AM exhibited the lowest solubility and highest turbidity than NM and KM as the temperature was higher than 40 °C, indicating that AM is easily to be denatured and aggregated. Circular dichroism (CD) analysis showed that both acidic and alkaline pH treatments led to conformational changes of myosin, together with α-helix content variations. When pH was readjusted to neutral, KM recovered its structure similar to NM, while AM failed to refold to its native state. NM exhibited the highest storage modulus (G′) at 90 °C, while AM revealed the lowestG′ value. Furthermore, AM did not change obviously during heating, especially at the gelling temperature range (60–90 °C). These results strongly suggested that acidic treatment led to an irreversible conformational change in myosin, consequently induced a fierce denaturation and aggregation at the initial stage of heating, and eventually led to a complete loss of gel-forming ability. Alkaline pH-shifting, on the other hand is thus more feasible for protein recovery from blue round scads.