Isolation and characterization of alpha, beta-momorcharins

Two ribosome - inactivating proteins(RIP's), alpha - and beta - momorcharin (alpha - and beta - 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 S ephadex G - 75. The molecular weights of the purified proteins as determine d by ESI - MS and MALDI - TOF - MS were 28625(alpha - MMC),29076(beta - MMC ) and 28795(alpha - MMC),29074(beta - MMC), respectively. Both of them were found to be glycoproteins and have pi values of 9.10(alpha - MMC) and 9. 3 2 (beta - 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 a nd N - terminal amino acid sequence of beta - MMC are described.