PURIFICATION AND CHARACTERIZATION OF FLAVONE-SPECIFIC BETA-GLUCURONIDASE FROM CALLUS-CULTURES OF SCUTELLARIA-BAICALENSIS-GEORGI

beta-Glucuronidase from callus cultures of Scutellaria baicalensis Geo rgi was purified to apparent homogeneity by fractionated ammonium-sulf ate precipitation and chromatography on diethylaminoethyl-cellulose, h ydroxylapatite and baicalin-conjugated Sepharose 6B. A 650-fold purifi cation was obtained by this purification system. When subjected to sod ium dodecyl sulfate-polyacrylamide gel electrophoresis the purified pr otein migrated as a single band with a molecular mass of 55 kDa. We de termined that the native enzyme has a molecular mass of 230 kDa using gel-filtration chromatography. These results suggested that the enzyme exists as a homotetramer composed of four identical 55-kDa subunits. The enzyme showed a broad pH optimum between 7.0 and 8.0. The K-m valu es were 9 mu M, 10 mu M, 30 mu M and 40 mu M for luteolin 3'-O-beta-D- glucuronide, baicalin, wogonin 7-O-beta-D-glucoronide and oroxlin 7-O- beta-D-glucuronide, respectively. The enzyme was most active with flav one 7-O-beta-D-glucuronides.