豆薯种子中两种蛋白质的分离纯化及其性质研究

豆薯（Ｐａｃｈｙｒｒｈｉｚｕｓｅｒｏｓｕｓ）种子经磷酸盐缓冲液抽提，Ｓ－ＳｅｐｈａｒｏｓｅＦａｓｔＦｌｏｗ柱，ＤＥ－５２纤维素柱和ＳｅｐｈａｄｅｘＧ－７５柱层析，提取出两种高纯度的蛋白成分，命名为ＰａｃｈｙｒｉｎⅠ和Ⅱ．ＳＤＳ－ＰＡＧＥ测得其分子量分别为３３ｋＤ和１４．５ｋＤ，但ＨＰＬＣ分子筛的结果显示ＰａｃｈｙｒｉｎⅡ的分子量为２８ｋＤ，无论在还原条件下，还是在非还原条件下，ＰａｃｈｙｒｉｎⅡ电泳的结果都完全相同，表明该蛋白的亚基不是以二硫键相连。两种蛋白的等电点分别为４．５和６．５．用酸解法测定了它们的氨基酸组成。在无细胞体系中，它们对蛋白合成有较弱的抑制活性，显示它们可能是核糖体失活蛋白（ＲＩＰｓ）家族中的新成员。

Purification. and Characterization of New Proteins from the Seeds of Pachyrrhizus erosus

From the seeds of Parhyrrhizus erosus, two protein constituents named Pachyrin Ⅰand Ⅱ have been isolate and purified by extraction with PB buffer,S-Sepharose Fast Flow, DE52 cellulose and Sephadex G-75 column chromatography. These two proteins are homogeneous as proved by SDS-PAGE , IEF and HPLC experiments. The molecular weights are about 33 kD and 14. 5 kD by SDS-PAGE. But using HPLC analyses,the mr value of Pachyrin Ⅱ in 28 kD. This indicates that Pachyrin Ⅱ are composed of two chains. The same pattern was seen under both reducing and nonreducing conditions,demonstrating that there is no disuifide bond between them.The isoelectric points are 4. 5 and 6. 5 respectively. The amino acid compositions have been determined. In cell-free system,the two proteins display certain inhibitory activities to protein systhesis and are possible to be new members of ribosome-inactivating protein (RIP) family.