Concerning the location and persistence of soil urease

Urease activity in soil is persistent for long periods under low water, low temperature, and sterile regimes, and it has been suggested that some form of enzyme-protective mechanism exists in soil. Dublin soil was sonicated in water and extracted by adding a mixture of salts. Urease activity is associated with the organomineral complex thus obtained and is resistant to the activities of proteolytic enzymes. Clay-free soil organic matter prepared subsequently by filtration also exhibits urease activity which is resistant to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis. Models consisting of enzymes with bentonite and lignin were found to mimic this resistance to proteolysis. A model system is presented which suggests both the origin and location of soil ureases and a reason for their persistence in nature