苦瓜子蛋白的分离纯化及其性质研究

Isolation and Characterization of α, β- Momorcharins

从苦瓜种子的粗提物苦瓜子蛋白丙酮分级沉淀干粉中,用CM-Sephadex C-50和SephadexG-75分离得到了两个核糖体失活蛋白,α-苦瓜子蛋白(α-momorcharin,α-MMC)和β-苦瓜子蛋白(β-momorcharin,β-MMC),其等电点分别为9.10(α-MMC),9.32(β-MMC).用ESI-MS和MALDI-TOF-MS测定它们的分子量,分别为28625(α-MMC),29076(β-MMC)(+Na,29099);,28795(α-MMC),29074.7(β-MMC).它们都是糖蛋白.其生物活性的分析测定表明,都属于RNA N-糖苷酶.本文重点对β-苦瓜子蛋白的分离纯化及其性质进行详细报道,并对其N-端部分的氨基酸顺序进行了测定.

Two ribosome- inactivating proteins(RIP's) , α- and β - momorcharin(α - and β - MMC) have been isolated from the seeds of bitter melon ( Momordica charantia ), a traditional Chinese folk medicine. This was done by acetone fractionation and chromatographies on CM - Sephadex C - 50 and Sephadex G - 75. The molecular weights of the purified proteins as determined by ESI - MS and MALDI -TOF-MS were 28625(α - MMC),29076(β - MMC)and 28795(α - MMC),29074(β - MMC), respectively. Both of them were found to be glycoproteins and have pI values of 9.10(α - MMC) and 9. 32 (β - MMC) . Biological activity assay revealed both of them were RNAN - glycosidase and depurinate 28S rRNA in the ribosomes in a manner identical to that of trichosanthin. Here the isolation, physicochemical properties and N - terminal amino acid sequence of β- MMC are described.