Characterization of urease from Sporosarcina ureae

Alkaline stable (pH 7.75-12.5) urease from Sporosarcina ureae was purified over 400-fold by ion exchange and hydrophobic interaction chromatography. The cytoplasmic enzyme was remarkably active with a specific activity of greater than 9300 mumol urea degraded min-1 mg protein-1 at pH 7.5, where it has optimal activity. Although S. ureae is closely related to Bacillus pasteurii, known to possess a homopolymeric urease containing 1 nickel per subunit [M(r) = 65000], the S. ureae enzyme is comprised of three subunits [apparent M(r) = 63,100 (alpha), 14,500 (beta), and 8500 (gamma)] in an estimated alpha beta gamma 2 stoichiometry and contains 2.1 +/- 0.6 nickel ions per alpha beta gamma 2 unit as measured by atomic absorption spectrometry. Stationary phase cultures sometimes possessed low levels of urease activity, but the specific activity of cell extracts of partially purified urease preparations from such cultures could be elevated by heat treatment, dilution, or dialysis to values comparable to those observed in samples from exponentially grown cells.