不同种类酸诱导罗非鱼肌球蛋白去折叠行为的研究

以罗非鱼肉为原料,采用硫酸铵沉淀法提取肌球蛋白,固定蛋白浓度2 mg/mL,分别采用HCl、H2SO4、H3PO4和C6H8O7(Citric acid)调节体系pH值为2.0、3.0,以溶解度、表面疏水性、总巯基和活性巯基含量、色氨酸荧光光谱和圆二色谱为指标,研究不同种类酸诱导肌球蛋白去折叠过程中分子结构的变化.结果表明,肌球蛋白经过酸处理后分子部分展开,表面疏水性和活性巯基含量增加,色氨酸荧光强度下降、α-螺旋含量降低,且pH2.0条件下处理的肌球蛋白去折叠程度大于pH3.0;比较而言,pH2.0条件下,C6H8O7处理的肌球蛋白展开程度最大,α-螺旋含量由41.7％降低至20.5％;pH3.0条件下H2SO4处理的肌球蛋白结构展开程度最大,溶解性下降最明显;而HC1诱导的肌球蛋白去折叠过程中,蛋白分子变性程度最小,α-螺旋含量下降不明显,分子稳定性较好,呈“熔球态”构象.

Unfolding beheavior of Tilapia myosin induced by different acids

Myosin was extracted from Tilapia meat using ammonium sulfate precipitation in this study. Theacid -induced unfolding was carried out at pH2.0 and pH 3.0 by HCl, H2SO4, H3PO4 and C6H8O7, at protein concentration of 2 mg/mL. Solubility, surfacehydrophobicity, total and active sulfhydryl content, intrinsic tryptophanfluorescence spectra and circular dichroism were determined, changes of conformation of tilapia myosin during acidinduced unfolding were studied. Results showed that surface hydrophobicity and reactive SH content of myosin increased by different acid treatments, tryptophan fluorescence intensity and -helix content decreased, suggesting acid-induced unfolding of myosin. And at pH 2.0, myosin had a greater degree of unfolding than that at pH 3.0. Incomparison, the C6H8O7-induced unfolding degree was the highest at pH 2.0 and the -helix content of myosin decreased from 41.7% to 20.5%. However, at pH 3.0, the H2SO4-induced unfolding degree was the highest, and resulted in the significantly decline of solubility. The denaturation of myosin during HCl-induced unfolding was the minimum, and no obvious change of -helix content was obtained, indicating that myosin molecules was stable and retained a molten globulestate