Summary: Urease was purified (4126-fold) from (NRRL 003) to a homologous enzyme preparation with a specific activity of 1341 μmol min (mg protein). One species of urease was detected in , with = 3.0 mM, native molecular mass 250 000 Da, pH optimum of 8.0 and a high specificity for urea. Hydroxyurea was a strong competitive inhibitor of urease activity, while -methylurea acted as a weak uncompetitive inhibitor, based on Lineweaver-Burk and Eadie-Hoftstee plots. The activity of urease was enhanced by, but not dependent on, the presence of NaEDTA, DL-dithiothreitol (≤ 0.1 to 5.0 mM), Ca, Ba and citrate (2 to 20 mM). Urease activity was not affected by Na, K, Cl, Br, acetate or nitrate (2 to 20 mM), but was significantly decreased in the presence of Li, Ni, Mg, Zn or I. Urease activity decreased 26.0% after 30 min at 65 °C, and 86.5% and 100.0% after 5 and 1 min at 80 and 100 °C, respectively. Urease activity decreased 30.5% after 90 d at 4 °C and 21.0% after 28 d at −20 or −80 °C.


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