Expression, characterization and application of thermostable beta-glucuronidase from Thermotoga maritima / 生物工程学报

ABSTRACT

The gene of beta-glucuronidase from Thermotoga maritima was cloned into the plasmid pHsh, and expressed in Escherichia coli JM109. The recombinant protein was purified to homogeneity by a simple step, heat treatment. The recombinant enzyme had a molecular mass of 65.9 kD. The optimal activity of beta-glucuronidase was found at pH 5.0 and 80 degrees C. The purified enzyme was stable over a pH range from 5.8 to 8.2 and had a half life of 2 h at 80 degrees C. The kinetic experiments at 80 degrees C with p-nitrophenyl-beta- glucuronide as substrate gave a K(m) and V(max) of 0.18 mmol/L and 312 u per mg of protein. The purified enzyme could transform glycyrrhizin to glycyrrhetinic acid.