Partial purification and some properties of urease from the alkaliphilic cyanobacteriumNostoc calcicola

Urease extracted from an alkaliphilic diazotrophic cyanobacteriumNostoc calcicola was partially purified and some of its properties were studied. Urease purified 39-fold from the crude enzyme extract showed its optimum activity at pH 7.5 and at 40°C with aK _m value of 120 μmol/L. The enzyme was found to be sensitive to metal cations, particularly Hg²⁺, Ag⁺ and Cu²⁺. 4-Hydroxymercuribenzoate (a mercapto-group inhibitor) and acetohydroxamic acid (a chelating agent of nickel) inhibited, the enzyme activity completely. These results suggest the involvement of an SH-group and Ni²⁺ in the activity of urease fromN. calcicola.