KINETIC-BEHAVIOR OF SYNTHETIC ORGANO-COMPLEXES AND ORGANO-MINERAL-UREASE COMPLEXES

A study was conducted for characterizing the properties and the cataly tic behavior of enzymatic complexes that are considered analogues of t hose usually present in soil. Active enzymatic complexes were formed a t 10 degrees C by interaction for 1 h of urease and tannic acid with a nd without Fe ions and OH-Al polymers. The enzymatic complexes obtaine d in the presence of Fe3+ ions and OH-Al species showed higher activit y levels than urease-tannate complexes. The pH optimum of immobilized urease did not differ significantly from that of free urease, except f or the tannate complexes, which showed a pH optimum slightly shifted u pwards by approximate to 0.5 units. Immobilized urease displayed the h ighest activity in a wider range of temperatures (60-80 degrees C) com pared with the free enzyme. The free enzyme showed a marked reduction in activity above 70 degrees C. Higher values of energy of activation (E(a)), enthalpy of activation (Delta H-a), and the kinetic parameter (K-m) were obtained for urease immobilized on tannate molecules. On th e contrary, the complexes obtained with Fe3+ and OH-Al species display ed kinetic and thermodynamic parameters similar to those of the free e nzyme. Immobilized urease showed a catalytic behavior similar to the f ree enzyme, when the interaction with tannic acid occurred in the pres ence of Fe3+ ions and OH-Al polymers. Evidently, both Fe ions and OH-A l species favored the formation of enzymatic complexes in which confor mational and catalytic features of the enzyme remained practically unc hanged.