Exploring Wheat Leaf Urease for a Sustainable Approach: Purification, Kinetics, and Thermal Stability...

The urease enzyme has an inevitable application in cereal crops, particularly in response to foliar urea application. A holistic and novel approach was employed in the present work with the aim to purify and characterize the wheat leaf urease. This will help in exploring and enhancing its activity in assimilation of foliar urea application and a move towards sustainability. Wheat urease was purified to electrophoretic homogeneity with a 41.98 fold purification and 36.3% recovery. The molecular weight of the native enzyme was found to be ~ 290 kDa by Gel Filtration Chromatography (GFC), and a single band in Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) of ~ 103 kDa deduced its homotrimeric nature. The enzyme had a K_m of 1.0 mM, V_max of 63.25 units mL^-1, turnover number of 30.26 min^-1, and a specificity constant of 504.33 M^-1 sec^-1. Further, the optimum pH was 7.5 with 40 °C optimum temperature. The E_a of the purified urease was 61.36 kJ mol^-1, with the E_d as 104.3 kJ mol^-1. The half-life and D-value decreased with an increase in temperature owing to the rapid loss of its catalytic activity. The z-value was calculated as 44.6 °C. The thermodynamic study revealed the interplay between ΔH, ΔG and ΔS during enzyme deactivation. Histidine was found to be present at the active site and Nickel enhanced the urease activity, whereas copper displayed an inhibitory effect. Hence, this study of wheat urease offers novel insights into an enzyme that has remained largely unexplored despite its inevitable importance in cereal crops. The measures for enhancing its activity in vivo can also be abstracted from this study.