Effect of temperature, pH and Hg2+ and Pb2+ traces in dehydrogenase and urease activities of a soil from Évora region

Abstract

Enzyme activities are often used as in­dicator of soil quality. This study reports on dehydrogenase (EC 1.1.1) and urease (EC 3.5.1.5) activities of a soil under Olea europaea L. from Évora region. Kinetic constants Km and Vmax were determined using p-iodonitrotetrazolium chloride (INT) and urea, respectively. Effects of pH, temperature and Hg²⁺ and Pb²⁺ traces on both activities were determined.

Maximal activity was obtained at pH = 8.5 and 40ºC, K_m = 0.5 mM and V_max=5,4µmol min^-1 g^-1 , for dehydro­genase and at pH = 10 and 37 ºC, Km = 25.7 mM and V_max = 2.0x10^-2 µmol min^-1 g^-1, for urease. These activities were in­hibited by different concentrations of Hg²⁺, but only the urease activity was in­hibited by Pb²⁺. Results of this study are comparable to those reported in the litera­ture for these enzymes.