中药决明子蛋白质的提取分离及部分一级结构的测定

Extraction and Separation of Protein from Cassia Seed and Determination of Its Partial Primary Structure

决明子 (CassiaobtusifoliaL)的蛋白质含量比较丰富 ,其中含有人体必需的各种氨基酸 .通过十二烷基硫酸钠 聚丙烯酰胺凝胶电泳 (SDS -PAGE)分析的结果表明 ,决明子非还原态蛋白质主要是由相对分子质量 (Mr)为 4 2、4 0和 38kd的蛋白质组成 ,还原态主要由Mr 为 2 4和 16.5kd的两条肽链组成 .采用硫酸铵盐析分级法提取蛋白质的结果表明 ,当硫酸铵饱和度为 4 0 %～ 55%时 ,所提取的蛋白质 (P55)得率最高 .对由P55分离纯化所得的主要组分PS 的N端部分进行测序及同源分析 ,结果显示该序列与人体载脂蛋白B有一些相关性 ,并提示决明子蛋白质或有可能通过参与体内脂质的代谢而起到降脂的作用 .

The protein content of cassia seed ( Cassia obtusifolia L) is 18.69%, in which there are all kinds of amino acids that are indispensable to human body. SDS?PAGE analysis showed that protein of cassia seed mainly consists of three classes of protein, the molecular weight of which are 42 kd, 40 kd and 38 kd respectively. When mercaptoethanol was added to the samples, they decomposed into two classes of peptide. Their molecular weight are 24 kd and 16.5 kd respectively. The protein of cassia seed was extracted by ammonium sulfate fractionation and the high quantity of protein was obtained at 40%～55% saturation of ammonium sulfate. The sequence of N terminal 20 amino acids of Ps, one of the components of the peptides, was determined. Results showed that, to a certain degree, there were homology between the P S and apolipoprotein B in the sequence. As a result, it was possible for protein of cassia seed to perform the lipid lowering action through its participation of the lipid metabolism.