DETERMINATION OF THE UREASE ACTIVITY AND RELATIVE INHIBITION IN THE PRESENCE OF SOME METAL IONS: A MICROCALORIMETRIC STUDY

Batch microcalorimetry has been employed to obtain a calibration curve for the enzymatic activity of urease in solution. This method is simplier, more reliable and easier to handle than the more common techniques (spectrophotometry and potentiometry), because it is based on direct investigation of the enzymatic reaction. By comparison with calorimetric studies employing the thermistor combined with the immobilized, enzyme, this method also allows the catalytic activity to be measured. Variations in the urease activity in the presence of nine metal ions [Hg(II), Ag(I), Cu(II),Zn(II), Cd(II), Ni(II), Co(II), Mn(II) and Mg(II)] are also described. A graphic method has been devised for immediate identification of the minimum inhibitor concentration,determining the start, 50% and complete inhibition of ureasic activity.