Background: Urease is a nickel-dependent enzyme that catalyzes the hydrolysis of urea into ammonia and carbon dioxide, facilitating nitrogen transformation and enhancing its bioavailability for plant uptake. Beyond its agronomic relevance, urease also serves as a defense protein in certain plants and is produced by various microorganisms. This study focused on the purification and characterization of urease enzymes isolated from three sprouted melon varieties: Watermelon, Whitemelon, and Blackmelon sourced from the Lapai market in Niger State, Nigeria.
Methods: The extraction process involved sequential steps: ammonium sulfate precipitation, dialysis, gel filtration chromatography, and SDS-PAGE analysis. Enzyme activity was assessed under varying pH levels and temperatures and in the presence of selected metal ions. The molecular weights of the purified enzymes were determined using SDS-PAGE.
Results: Purification folds were 4.0, 2.5, and 1.6, with corresponding yields of 19.5%, 18.4%, and 19.2% for Watermelon, Whitemelon, and Blackmelon, respectively. Optimal pH values were 6.0 for White and Blackmelon and 7.5 for Watermelon. The temperature optima were recorded at 30°C (Watermelon), 40°C (Blackmelon), and 50°C (Whitemelon). SDS-PAGE revealed distinct protein bands at 55, 38, and 35 kDa for Watermelon and White melon, whereas no defined band was observed for Black melon. Nickel ions significantly enhanced enzyme activity, while Mg²⁺, Hg²⁺, EDTA, Ba²⁺, Ca²⁺, and K⁺ exhibited inhibitory effects in decreasing order. Kinetic parameters revealed Vmax values of 0.000611, 0.000410, and 0.000163 U/sec for watermelon, blackmelon, and whitemelon, respectively, with corresponding Km values of 0.0341, 0.0469, and 0.0021 mg/mL.
Conclusion: These findings suggest that urease derived from these sprouted melon varieties holds potential for immobilization and utilization in urea biosensing and other urease-based biotechnological applications.
urease, sprouted, melon, purification, characterization
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