Purification and Characterization of Intracellular Urease Enzyme Isolated from Rhizopus oryzae

Extraction and purification of the intracellular urease of Rhizopus oryzae was carried out through different steps. Production and crushing the collected cells and preparation of the cell free homogenate were estimated. The intracellular R. oryzae urease was purified to homogeneity by salting out with ammonium sulphate, dialysis and passage through chromatography resins (Sephdex G-200 column, Sephdex G-100 and Diethylaminoethyl cellulose column) and test for purity by simple polyacrylamide gel electrophoresis technique. The purified enzyme resulted in 622 fold by native molecular size of 172 kDa, exhibited a specific activity in the presence of urea of 112 U mg-1 protein with the recovery of 26%. Studying factors affecting the activity of the purified urease enzyme resulted in: There was a proportional increase of enzyme activity corresponding to the increase of the enzyme concentration. The optimum concentration of urea was (20 μg mL-1). An optimum temperature was 55oC. The purified enzyme was most active at pH 7. Potassium, zinc and cupper salts, each inhibited activity of the purified enzyme. Urease activity was enhanced by the presence of magnesium, manganese and calcium salts, but inhibited completely by mercury. The reversible urease inhibitors, ferrous and cobalt salts, blocked enzyme activity in the crude mycelial fraction when added at a concentration of 10-3 M.