ENTHALPIMETRIC AND COLORIMETRIC DETERMINATIONS OF THE INHIBITION CONSTANT FOR THE INHIBITION OF UREASE BY BORIC-ACID

Continuous enthalpimetric and fixed-time-point colorimetric analytical studies of jack bean urease-catalyzed hydrolysis of urea uninhibited and inhibited by boric acid were performed. The effect of boric acid o n urease activity was studied in 100 mM phosphate buffer of pH 7 (H3PO 4+NaOH, 2 mM EDTA) at 25 degrees C. The inhibition constant of boric a cid was obtained with use of differential and integration methods. It was found that boric acid is a simple competitive inhibitor of urease. The methods produced comparable values of the inhibition constant K-i : the former 0.19 mM and the latter 0.18 mM.