The $eta$-glucuronidase (GUS) gene from Lactobacillus brevis RO1 was cloned and expressed in Escherichia coli GMS407. The GUS gene was composed of 1,812 bp, encoding a 603-amino-acid protein belonging to glycosyl hydrolase family 2 with three conserved domains. The amino acid similarity was higher than 70% with the $eta$-glucuronidases of various microorganisms, yet less than 58% with the $eta$-glucuronidase of L. gasseri ADH. Overexpression and purification of the GUS was performed in $eta$-glucuronidase-deficient E. coli GMS407. The purified GUS protein was 71 kDa and showed 1,284 U/mg of specific activity at optimum conditions of pH 5.0 and $37^{circ}C$. At $37^{circ}C$, the GUS remained stable for 80 min at pH values ranging from 5.0 to 8.0. The purified enzyme exhibited a half-life of 1 h at $60^{circ}C$ and more than 2 h at $50^{circ}C$. When the purified GUS was applied to transform baicalin and wogonoside into their corresponding aglycones, $150;{mu}M$ of baicalin and $125;{mu}M$ of wogonoside were completely transformed into baicalein and wogonin, respectively, within 3 h.