Urease-induced crystallization in synthetic urine.

The urease-induced crystallization of magnesium ammonium phosphate and calcium phosphate was studied at different alkalinization degrees by incubating synthetic urine with increasing Jack Bean urease concentrations. The crystallization was studied as precipitation on glass rods immersed in synthetic urine. The calcium phosphate precipitation on the glass rods occurred when the pH reached 6.8. Magnesium ammonium phosphate precipitation occurred when the pH reached 7.0. The maximal crystallization occurred at a pH between 7.5 and 8.0; at higher pHs the precipitation was considerably lower. The possible mechanisms and clinical implications behind this narrow pH optimum for urease-induced crystallization, which also have important implications for future experimental studies, are discussed.