Biochemical studies on citrullus vulgaris urease: stability and reactivation by some reducing agents

Watermelon [Citrullus vulgaris cv. "Giza 1"] urease was inhibited by the divalent metal ions. Mg2+, Ca2+, Ba2+ [10 mM] and Mn2+ [0.02 mM] partially inhibited the enzyme with 15.9, 28.8, 8.0 and 12.0% inhibition, respectively. The heavy metal ions inhibited the enzyme in the order of Hg2+ > Cd2+ > Zn2+ > Cu2+ > Co2+ > Ni2+. Thiols as reducing agents at low concentrations ranging from 0.0001 to 0.01 mM caused activation of the enzyme and preserved its activity. The enzyme was stored in 0.01 mM dithiothreitol and 0.1% penicillin- streptomycin. It was stable and free of bacterial contamination for 6 moths. The specification of this enzyme meets the prerequisites needed for preparation of diagnostic urea kit