THERMAL INVESTIGATIONS OF ENZYME-CATALYZED REACTIONS FOR DETECTION OFHEAVY-METALS IN THE CASE OF CADMIUM

The present work gives the results of extensive calorimetric measureme nts to determine the inhibitory effect of cadmium ions on enzymatic ur ea hydrolysis. Three milligrams of urease and 10 mmol urea (kg solutio n)(-1) were found to be the optimum reaction conditions in 0.05 M HEPE S buffer (pH 6.6). A correlation between the initial rate v(0) and the cadmium concentration in the ppm range can be demonstrated by determi nation of the initial slope of the calorimetric measuring curves. By d etermination of the enzyme kinetic data, a contribution to detailed in formation on the inhibitor mechanism of cadmium can be made with these results.