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 fractionaction 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.

Key words: SEPARATION, PURIFICATION, GLYCOSIDASE, GLYCOPROTEIN, BIOLOGICAL ACTIVITY, AMINO ACID SEQUENCE ANALYSIS, MOMORDICA CHARANTIA, CUCURBITACEAE