Studies on urea hydrolysis. Part 2. Effects of some heavy metals on urease activity

The effect of some heavy metals on the urease activity was studied in a pure system using jack bean urease (JBU). While Mn showed no effect, copper reduced the enzyme activity more than did Zn or Fe at high concentrations (100 ppm). At a low concentration, iron reduced the enzyme activity more than at a high concentration. Inhibition of the urease activity was induced by less than 0.1 ppm Fe, 0.5 ppm Cu, and 10.0 ppm Zn. In the soil, these heavy metals inhibited the JBU in this order: Fe++ greater than Cu++ greater than Zn++. The possibility is discussed of using heavy metals to delay urea hydrolysis in soils.