Abstract
The rhyzome of ginger (Zingiber officinale) has a high proteolytic activity. The ginger protease was separated by chromatography on DEAE-cellulose into two fractions, GP I and GP II, but they were not distinguishable from each other on sephadex gel-filtration. GP I and GP II were purified to 10- and 13-folds, respectively, by the ammonium sulfate fractionation and the subsequent column chromatography using DEAE-cellulose and hydroxyapatite. The electrophoretic mobilities of the two proteases were different from each other. Their crystal forms were found to be hexagonal plates.
The gel-filtration and electrophoretic analyses indicated the uniformity of the two proteases. Their molecular weights were estimated to be about 22, 500 each, according to the Sephadex G-100 gelfiltration. The general properties of both enzymes were shown to be almost identical with regard to the pH optimum (6.5 to 7.0), the activation by sulfhydryl compounds, the inhibition by heavy metal ions and sulfhydryl reagents such as iodoacetate and iodoacetoamide, and the non-inhibition by dithionitrobenzonate and p-chloromercuribenzonate. The enzymes were not active in the absence of sulfhydryl compounds, but their activities were fully restored by addition of cysteine, β-mercaptoethanol or reduced glutathione. It is noted that the inhibition by heavy metal ions such as Ag+ and Ni++, and the activation by sulfhydryl compounds were observed more clearly for GP I than for GP II.
