Purification and characterization of a 28-kDa major protein from ginseng root

A major protein was isolated from ginseng root (Panax ginseng C.A. Meyer) using a combination of ammonium sulfate fractionation, gel filtration chromatography, ion-exchange FPLC, and fast performance liquid chromatofocusing. Electrophoretic and gel permeation chromatographic studies revealed that the major protein, GMP, is composed of two subunits of approximately 28 kDa. During purification, it was found that the elution profiles of GMP from gel filtration chromatography were significantly different, depending on the ionic strength of buffers used. GMP in a buffer of low ionic strength was isolated as a complex with carbohydrate, which could be only dissociated at high ionic strength. Carbohydrate composition in GMP detected by gas chromatography varied, depending on the isolation method of the protein from ginseng roots. These results suggest that carbohydrates are bound non-covalently to GMP whose amino acid composition analysis showed high amounts of acidic amino acids.