Integrated purification and immobilization of glutamate decarboxylase

Glutamate decarboxylase (GAD) is the key enzyme for the production of gamma-aminobutyric acid (GABA), a multifunctional agent which biosynthesis has attracted intense interest. Though immobilized GAD favors the preparation of GABA in several ways, its efficiency and enzyme activity recovery are damaged by the separation of purification and immobilization of enzyme. In order to simplified the process and reduce loss of enzyme, integrated purification and immobilization of GAD by one-step affinity absorption was carried out and the obtained immobilized GAD was characterized. The one-step absorption made 83.8% active GAD immobilized, which improved the temperature- and pH-stability of GAD to some extent. The fixed enzyme exhibited optimum temperature similar to the free while its optimal pH was higher than that of the free, pH 5.6 comparing with pH 4.1. Km of the immobilized GAD and the free were about the same value. The immobilized GAD retained about full activity after three-time utilization and about 65% after the nine-time. These results demonstrated the coupled immobilization method not only simplified the process but kept GAD a good catalyst for the biosynthesis of GABA.