Bioactive protein from rhizomes of Zingiber ottensii Valeton

Abstract

The objectives of this study were to find out bioactive protein from Zingiber ottensii rhizome and study properties of purified protein. Protein from the rhizome was isolated using 20 mM Tris-HCl buffer, salting out with 80% (NH4)2SO4, and purified by stepwise eluted (1 M NaCl) SP sepharose chromatography. Five fractions obtained from purification step were unbound, F25, F50, F75, and F100 which the highest protein content was found in the F50 fraction. Results form native and reducing SDS-PAGE indicated that the F50 was single protein contained at least three subunits with sizes 32.5, 15.2, and 13.8 kDa. Periodic staining and phenol-sulfuric assay showed that the F50 was glycoprotein and contained 26.30 1.01% (by weight) carbohydrate moiety, respectively. By trypsinized and LC-MS/MS analysis, it was found that amino acid sequence of F50 was the most resemble to cysteine protease. Bioassay results indicated that the F50 contained -glucosidase inhibitory activity which the maximum inhibiton, IC50, and Ki were 100%, 30.15 g/ml, and 140 mol, respectively. The activity was stable at pH range 2-10 and at temperature up to 65oC. Furthermore, the F50 could inhibit growth of three plant pathogenic fungi, Fusarium oxysporum, Exserohilum turicicum, Colectrotrichum cassiicola, at a concentration of 23.6 to 42.7 g, but no any effect on test bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The F50 could also inhibit hepatoma cancer (HEP-G2; IC50 = 1.130 g) and colon cancer (SW620; IC50 = 5.370 g) proliferation. This could be concluded that a glycoprotein from Z. ottensii was successfully purified and its bioactivities were also characterized