title: Employment of pumpkin (Cucumis melo) urease entrapped in alginate beads for quantitation of cadmium in aqueous media.
abstract: The potential of employment of free as well as alginate-immobilized urease for the quantitation of cadmium (Cd(2+)) was explored. Urease from the seeds of pumpkin (Cucumis melo) was purified to apparent homogeneity by heat treatment at 48 +/- 0.1 degrees C and gel filtration through Sephadex G-200. The purified enzyme exhibited a single band on native PAGE under coomassie brilliant blue and silver staining. The enzyme entrapped in 3.5% alginate beads (with 86% immobilization) exhibited no leaching over a period of 15 days at 4 degrees C. Urease-catalyzed urea hydrolysis by both soluble and immobilized enzyme revealed a dependence on the inhibitor concentration. The inhibition caused by Cd(2+) was non-competitive and the interaction of Cd(2+) with the enzyme was irreversible as the activity could not be restored by dialysis. The time-dependent inhibition both in the presence and in absence of substrate revealed a biphasic inhibition of the activity. The significance of the results is discussed.
authors.affiliation: Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi, India.
authors.forename: Om
authors.initials: O
authors.lastname: Prakash
authors.forename: Mahe
authors.initials: M
authors.lastname: Talat