Biocatalytic properties of a novel crude glycyrrhizin hydrolase from the liver of the domestic duck

A novel crude glycyrrhizin (GL) hydrolase preparation from the liver of domestic duck was used to produce glycyrrhetic acid monoglucuronide. To characterize the biocatalytic profiles of the crude enzyme, some effect factors were investigated. It had an apparent optimal pH of 6.0 and an optimal temperature at 55 °C. Most of the metal ions tested and ethylene diamine tetra acetic acid showed little effect on the crude enzyme activity except Cu2+. The enzyme was stable only at pH 6. It was more prone to inactivity at high pH conditions than at low pH conditions. It was stable at temperatures below 55 °C and it will lost 90% GL hydrolytic activity exposed at 70 °C. GL hydrolytic activity declined by 30% compared with the control in aqueous solution (buffer pH 6.0) when pre-equilibrated at 55 °C for 5 days. It indicated that the novel crude GL hydrolase preparation had good biocatalytic ability for selective hydrolysis of one glucuronic acid from GL.