초록
${\beta}$-Glucuronidase (EC 3.2.1.31) which hydrolizes D-glucuronate from ${\beta}$-D-glucuronide was purified from rat liver, using ammonium sulfate fractionation, DEAE-cellulose chromatography, Concanavalin-A Sepharose 4B chromatography and gel filtration on Sephadex G-200. This enzyme has the molecular weight of 280,000 daltons by gel filtration and 75,000 daltons by SDS-polyacrylamide gel electrophoresis. As its funtion is reverse of detoxification in the liver, the inhibition of the enzyme was tested with extracts of several food products and medicinal herbs, some are known as anti-cancer agents. Among them, Panax ginseng and Cortnellus shiiake inhibited the enzyme competitively and the $K_1$ values were $9.22 {\times}\;10^{-2}$ and 0.102 mg/ml, respectively. These inhibitors strongly bound to DEAE-cellulose. The negatively charged amino acids, L-aspartate and L-glutamate, inhibited the enzyme, and $K_1$ value of L-aspartate was 0.80 mM. The interaction between ${\beta}$-glucuronidase and p-nitrophenyl-${\beta}$-D-glucuronide was found to involve ionic forces by the effect of ionic strength on the kinetic constant, Vmax/Km. It was inferred from these findings that cationic group at the active center of the enzyme is probably involved in attacking the substrate.
