Partial Purification And Characterization Of Urease From Germinating Chickpea (Cicer Arietinum L.) Seed.
 

Sahela Pervin, Niranjan Kumar Sana^*, Md. Golam Sarowar Jahan, Md. Masudul Hasan Khan, Md. Rezaul Karim, Bidhan Chandra Sarkar and Ranajit Kumar Shaha
Department of Biochemistry & Molecular Biology,
University of Rajshahi, Rajshahi-6205, Bangladesh.

Urease, the urea-hydrolyzing enzyme, was identified abundantly in germinating chickpea (Cicer arietinum L.) seed. The enzyme was purified to homogeneity by the sequential steps of 20% acetone extraction, followed by 50% acetone fractionation, gel filtration on Sephadex G-200, and DEAE- cellulose chromatography. The purification fold was 44.99 with a final specific activity of 489.57 mMmin^-1mg^-1. The purified urease was a hexamer of identical subunits. The native enzyme had a molecular mass of 510 kDa (Gel filtration, Sephadex G-200) whereas subunit values of 85 kDa were determined on PAGE with sodium dodecyl sulfate. The optimum pH and temperature of the purified urease were 7.2 and 480C, respectively, using urea as substrate. The half-life of urease was 30 days in 50 mM phosphate buffer (pH 7.2) at 4⁰C. K_m value of the purified urease for urea was 3.1 mM. Urease activity was decreased by 50% within 5 minutes at 70⁰C. The optimum substrate (urea) concentration for urease was 25 mM. The enzyme showed the highest activity when incubated for 30 minutes at 48⁰C. Ca²⁺ enhanced urease activity by 120.47%, while Pb²⁺, Cu²⁺, Zn²⁺ and Hg²⁺ almost completely inhibited the urease activity.