Thermal Sensitivity and Kinetic Properties of Soil Urease

Thermal sensitivity, pH optima and reaction rate constants of urease in soils of the Indian Agricultural Research Institute farm were studied. Influence of different soil characteristics on the enzyme kinetics was also evaluated. Soil urease activity was not adversely affected between 40 and 70°C but at 80°C and higher temperatures the enzyme was completely inactivated. In buffered systems peak urease activity was observed at pH 6.6 and 9.25. Michaelis constant (Km) for the enzyme varied in different soils and out of the various soil characteristics studied, it was significantly and positively correlated with soluble salt content only.