A study of the effect of restriction supports on the stability of urease enzyme purified from Citrullus seeds colocynthis

Abstract

This study revealed that urease was immobilized by entrapment in gelatin and
calcium alginate, the ratios of immobilization were 89% and 80% respectively. The result
of immobilized urease characterization showed that the enzyme retained its original
activity when it was incubated at 70 ºC for 50 minutes. The maximum enzyme activity of
immobilized enzyme was 80 ºC and the optimum pH of activity was 7.5.
The study revealed that the Km and Vmax of the immobilized enzyme were 181
mM and 225 mM/Min. respectively, when the urea was used as a substrate.

As for the stability of storage for free and immobilized enzyme, the study showed
that the immobilized enzyme by gelatin lost 20% of its activity after 90 days from
keeping in phosphate buffer 50 mM, pH 8 at 4 ºC in comparison with free enzyme which
lost 50% under the same condition. The enzyme immobilized by gelatin retained its
original activity till the tenth use while the enzyme immobilized by calcium alginate
retained its original activity till the fourth use.