Urease enzyme (EC 3.5.1.5) catalyzes the hydrolysis of urea into carbon dioxide and ammonia. Urea is the main toxic metabolic products, and the removal of this excess is a major problem for patients suffering from renal failures. The applications of urease in biotechnology are the analysis of urea content in blood, urine, natural water and environmental wastewaters. The most effective way for analysis of urea content in aqueous solutions is immobilization of urease enzyme on a surface such as nanoparticles. One of this nanoparticles is Fe3O4 magnetic nanoparticles which are cheap, non-toxic, biocompatible, easy to prepare, fast separated by external magnetic field, nanosize and having high surface area. So, they have found wide applications in biotechnology and enzyme immobilization. Urease was immobilized on magnetic nanoparticles by adsorption method and the enzyme loading efficiency was 96%. The values of kinetic constants Km and Vmax for free enzyme and immobilized on Fe3O4 magnetic nanoparticles were determined by measurement of enzyme activity using conductometry method. For free urease Km and Vmax are found to be 2.122mM and 69.93μM/min, respectively. In the case of immobilized enzyme the values of Km and Vmax are found to be 1.31mM and 33.3μM/min, respectively. The results suggested that the immobilization of enzyme slightly increased the urease affinity to substrate but it also hindered accessibility of the urease active site.

Keywords