Carboxyl Fe3O4 magnetic microspheres were prepared by a chemical co-precipitation method with potassium permanganate oxidation

and glutamate decarboxylase (GAD) was immobilized by the carboxyl magnetic microspheres as a carrier. The magnetic microspheres were characterized by methods of thermogravimetry (TGA)

transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results indicated that the magnetic microspheres had 95.1% contents of magnetite

homogeneous size and superparamagnetic behavior. GAD was well wrapped up in the magnetic microspheres by Fourier transform infrared (FT-IR) analysis

VSM and X-ray diffraction (XRD). The magnetic microspheres had complete crystal structure

good magnetic response and strong superparamagnetic behaviors before and after GAD immobilization. The enzymatic properties of immobilized and free GAD were analyzed and compared. The results showed that immobilized GAD had better thermostability and pH resistance and retained more than 90% activity after ten repeated batches.