大米蛋白的酶水解机制研究——Ⅱ酶水解过程中蛋白质的组分变化

Mechanism of Enzymetic Hydrolysis of Rice Protein(Ⅱ):Change of Protein Components during Hydrolysis

凝胶色谱和高效液相色谱分析表明,大米蛋白在碱性蛋白酶Alcalase水解过程中,其可溶性蛋白组分的相对分子质量(Mr.)分布范围相对稳定,但Mr.1350u以下小分子组分的相对含量不断增加;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)分析显示,随着酶水解反应的进行,Mr.为57、39、26、22ku的亚基逐渐消失,而29ku和13ku两个亚基的含量相应增加,且这两个亚基表现出可抵抗酶水解的特性。氨基酸分析表明,酶解后残余物蛋白中胱氨酸、蛋氨酸等含硫氨基酸的含量显著高于可溶性蛋白中的含量。圆二色光谱(CD)分析显示,酶水解前后大米蛋白的二级结构发生显著变化,在残余物蛋白质组分中自由回转的比例高达71.3%,α-螺旋结构完全消失。

Analysis with gel chromatography and high performance liquid chromatography （HPLC） indicates that during enzymatic hydrolysis of rice protein, the range of relative molecular mass tions is not evidently changed but the content of small soluble composition is gradually （Mr.） of the soluble composiincreased. The results obtained by sodium dodecyl sulphate-polyacrylamide gel electrophoresis （SDS-PAGE） show that during the enzymatic hydrolysis of rice protein, 57KDa, 39KDa, 26KDa and 22KDa subunits in the rice protein would graduall but the contents of 29KDa and 13KDa subunits increase. After the enzymatic hydrolysis of rice protein, y disappear, the contents of cystine and methionine in the residue protein after the enzymatic hydrolysis are higher than those in the soluble protein. Circular dichroism （CD） spectrum exhibits evident change in the secondary structure of the rice protein, such as α - helix completely disappears and the ratio of random coil in the residual protein components builds up to 71.3%, etc.