Effect of Toluene on the Energy Barriers in Urease Activity of Soils

Distribution, salinity, kinetic and thermodynamic characteristics of urease activity in a vertisol profile

“…The Gibb free energy of activation, AG, (63.8 0.6 kJ mole -I ) of soil urease was the same with and without buffer at all depths. This value was higher than that reported earlier for soil and bacterial urease (c. 47 kJ mole-'; Dalal 1975b), but lower than that (101 kJ mole -I ) obtained in a clay loam soil (Perucci et al 1982). Since the energy functions, such as LW, and AS,, reflect the additive effects of all three reaction rates, k,, k, and k -, of the urea-urease system, interpretation of energy functions is difficult, particularly in a heterogeneous system, such as soil.…”

“…Since the energy functions, such as LW, and AS,, reflect the additive effects of all three reaction rates, k,, k, and k -, of the urea-urease system, interpretation of energy functions is difficult, particularly in a heterogeneous system, such as soil. Dalal (1975b) observed that AS, of soil urease measured in the presence of toluene, but without buffer, was significantly affected by clay content; E, or AH, were not related to any of the soil properties studied (pH, clay, organic C). Similar results were obtained in this study when buffer was not used.…”

Effects of Catechol and P-Benzoquinone on the Hydrolysis of Urea and Energy Barriers of Urease Activity in Soils

“…1). (1913), in Alberta, Dalal (1975) in Trinidad, and Zantua et al (197'7) (Sizer 1943;Fisher and Parks 1958;Dalal 1975;Bremner and Mulvaney 1978). Most of the values of Q'o calculated in this study were in agreement with the data found for biological systems where an increase in reaction rate by a factor of 1.3-3.5 has been reported for a rise of 10'C in temperature (Sizer 1943 Sizer (1939) and Sizer and Tytell (1941) …”

“…However, studies concerning the energy of activation, entropy of activation and free energy of activation of soil urease are quite limited (Rachinskii and Pelttser 1967;Gould et al 1973;Dalal 1975) …”

Nitrogen losses from added urea and urease activity of a clay-loam soil amended with crop residues

“…where k is rate constant (initial urease activity, ~tmoles-N/g of soil/h) 8,10,19,24 Since the purity of the enzyme plays no apparent role in determining E, 24, the E~ values were calculated by plotting log k versus 1/T from logarithmic form.…”