Heavy Metal Ions Inhibition of Jack Bean Urease: Potential for Rapid Contaminant Probing

Abstract

The kinetics of heavy metal ions inhibition of jack bean urease was studied by progress curve analysis in a reaction system without enzyme-inhibitor preincubation. The inhibition was found to be biphasic with an initial, small inhibitory phase changing over the time course of 5-10 min into a final linear steady state with a lower velocity. This time-dependent pattern was best described by mechanism B of slow-binding inhibition, involving the rapid formation of an EI complex that subsequently undergoes slow conversion to a more stable EI* complex. The kinetic parameters of the process, the inhibition constants Ki and Ki* and the forward k5 and reverse k6 rate constants for the conversion, were evaluated from the reaction progress curves by nonlinear regression treatment. Based on the values of the overall inhibition constant Ki*, the heavy metal ions were found to inhibit urease in the following decreasing order: Hg2+ > Cu2+ > Zn2+ > Cd2+ > Ni2+ > Pb2+ > Co2+ > Fe3+ > As3+. With the Ki* values as low as 1.9 nM for Hg2+ and 7.1 nM for Cu2+, 100-1000 times lower than those of the other ions, urease may be utilized as a bioindicator of the trace levels of these ions in environmental monitoring, bioprocess control or pharmaceutical analysis.

Synthesis, crystal structures, and urease inhibitory activities of two azido-bridged polynuclear copper(II) complexes with Schiff bases

“…Generally, the assay mixture, containing 25 lL of jack bean urease (10 kU/L) and 25 lL of the tested complexes [22] containing 500 mM urea and 0.002% phenol red were added and incubated at 37°C. The reaction time, which was required to produce enough ammonium carbonate to raise the pH of the Hepes buffer from 6.8 to 7.7, was measured by a micro-plate reader (570 nm) with the end-point being determined by the color of phenol red indicator.…”

Synthesis, characterization and crystal structures of a pair of azido-bridged polynuclear Schiff base copper(II) complexes with urease inhibitory activity

“…Generally, the assay mixture, containing 25 lL of jack bean urease (10 kU/L) and 25 lL of the tested complexes of various concentrations (dissolved in the solution of DMSO:H 2 O = 1:1 (v/v)), was preincubated for 1 h at 37°C in a 96-well assay plate. Then 0.2 mL of 100 mM Hepes (N- [2-hydroxyethyl]piperazine-N 0 -[2-ethanesulfonic acid]) buffer at pH 6.8 [18] containing 500 mM urea and 0.002% phenol red were added and incubated at 37°C. The reaction time, which was required to produce enough Table 1 Crystallographic data for complexes (1) and (2) Complexes…”

Effective Use of Plant-Derived Urease in the Field of Geoenvironmental/ Geotechnical Engineering

“…Heavy metals, such as Cu 2+ , Zn 2+ , Pb 2+ and Hg 2+ almost completely inhibit the enzyme activity. This has also been proved for pigeon pea urease [45] and jack bean urease [46,47]. The urease enzyme activity is completely inactivated when the concentration of Hg 2+ is high enough [48].…”