核糖体失活蛋白(RIP)是在植物中充分表征的特异性N-β-糖基化酶。它们的酶作用是破坏核糖体,从而阻断蛋白质翻译。最近,几个研究小组一直在努力筛选可食用植物中的这些毒素,以促进RIP作为生物技术工具和生物农药的使用,并克服公众的偏见。这里,已从AtriplexhortensisL.var的种子中分离出四个新的单体(1型)RIP。rubra,俗称食用红山菠菜。这些酶,命名为hortensin1,2,4和5,能够释放β-片段,像许多其他RIP一样,来自鲑鱼精子DNA的腺嘌呤,因此,充当多核苷酸:腺苷糖苷酶。在结构上,hortensins具有不同的分子量,并以不同的产率纯化(hortensin1,〜29.5kDa,每100克0.28毫克;霍丁素2,~29kDa,每100克0.29毫克;霍丁素4,~28.5kDa,每100克0.71毫克;和5~30kDa的hortenin,0.65mg/100g);只有好动蛋白2和4被糖基化。此外,主要的同种型(好动蛋白4和5)对人连续成胶质细胞瘤U87MG细胞系具有细胞毒性。此外,在这些毒素的存在下,U87MG细胞的形态变化表明细胞凋亡途径触发了细胞死亡,如核DNA片段(TUNEL测定)所示。
Ribosome inactivating proteins (RIPs) are specific N-β-glycosylases that are well-characterized in plants. Their enzymatic action is to damage ribosomes, thereby blocking protein translation. Recently, several research groups have been working on the screening for these toxins in edible plants to facilitate the use of RIPs as biotechnological tools and biopesticides and to overcome public prejudice. Here, four novel monomeric (type 1) RIPs have been isolated from the seeds of Atriplex hortensis L. var. rubra, which is commonly known as edible red mountain spinach. These enzymes, named hortensins 1, 2, 4, and 5, are able to release the β-fragment and, like many other RIPs, adenines from salmon sperm DNA, thus, acting as polynucleotide:adenosine glycosidases. Structurally, hortensins have a different molecular weight and are purified with different yields (hortensin 1, ~29.5 kDa, 0.28 mg per 100 g; hortensin 2, ~29 kDa, 0.29 mg per 100 g; hortensin 4, ~28.5 kDa, 0.71 mg per 100 g; and hortensin 5, ~30 kDa, 0.65 mg per 100 g); only hortensins 2 and 4 are glycosylated. Furthermore, the major isoforms (hortensins 4 and 5) are cytotoxic toward human continuous glioblastoma U87MG cell line. In addition, the morphological change in U87MG cells in the presence of these toxins is indicative of cell death triggered by the apoptotic pathway, as revealed by nuclear DNA fragmentation (TUNEL assay).