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We present experiments that show the inhibition of the catalytic activity of the enzyme urease on the chemical degradation of urea with copper ions. In addition, we demonstrate the efficiency of the antidotes 2,3-dimercapto-1-propanesulfonic acid (DMPS, 2,3-bis(sulfanyl)propane-1-sulfonic acid) and 2,5-dimercapto-1,3,4-thiadiazole (DMTD) on reactivation of urease by complexation of copper.
Solid aquo CoII, CuII and ZnII complexes of Schiff bases derived from amino acids and salicylaldehyde had been prepared, characterized and used as model enzymes of Urease. Using a pH-stat method, the kinetics of acid hydrolysis of urea and its derivative N,N′-diacetyl urea in the presence of the complexes had been studied in pH range of 4.91?6.19 at 300C and I = 0.10 mol dm-3 (KNO3). It was found that the hydrolytic reactions followed first order kinetics (pseudo-unimolecular) with respect to urea or N,N′-diacetyl urea concentration. The complexes enhanced the rate of hydrolysis markedly; the values of the second-order rate constants (kH) being 106 times greater than those found in the absence of the catalysts. Comparison showed that the complexes acted as better catalysts for urea [kH = (0.79?2.34)?102 dm3 mol-1 s-1] than N,N′-diacetyl urea [kH = (0.36?1.19)?102 dm3 mol-1 s-1] towards the hydrolysis reactions. The catalytic performance of the complexes was 30-100% greater in urea than in N,N′-diacetyl urea. The proposed mechanism involved the formation of mixed ligand chelate complex by replacement of two coordinated labile water molecules by NHR′ (R′= H or COCH3) and carbonyl group of urea or N,N′-diacetyl urea followed by nucleophilic and electrohilic attacks by H2O and H+ respectively. The average half-life period (t?) ranges for urea and N,N′-diacetyl urea hydrolysis were 450?676 and 529?807 seconds respectively. [CoII(Gly)(Sal)(H2O)3] was found as the most efficient catalyst towards urea hydrolysis reactions. This investigation would establish the potential catalytic role of the complexes in hydrolyzing urea and its derivative, and thereby would throw more light on hydrolytic mechanism of urease enzyme.
Pakistan Journal of Nutrition
A New in Vitro Enzymatic Method to Evaluate the Protective Effect of Phytic Acid Against Copper Ions2021 •
The effect of monovalent copper ions on enzymatic systems has hardly been studied to date; this is due to the low stability of monovalent copper ions in aqueous solutions, which led to the assumption that their concentration is negligible in biological systems. However, in an anaerobic atmosphere, and in the presence of a ligand that stabilizes the monovalent copper ions over the divalent copper ions, high and stable concentrations of monovalent copper ions can be reached. Moreover, the cell cytoplasm has a substantial concentration of potential stabilizers that can explain significant concentrations of monovalent copper ions in the cytoplasm. This study demonstrates the effect of monovalent and divalent copper ions on DNA polymerase, ligaseT4 DNA, the restriction enzymes EcoP15I and EcoR I, acid phosphatase, and α and βamylase enzymes. These systems were chosen because they can be monitored under conditions necessary for maintaining a stable concentration of monovalent copper ions,...
African Journal of …
Immobilization of urease on copper chelated EC-Tri beads and reversible adsorption2011 •
1998 •
Coordination …
Structural properties of the nickel ions in urease: novel insights into the catalytic and inhibition mechanisms1999 •
2013 •
In order to develop new pharmaceutical agents, the Schiff base ligand, 2-{[(2-{[(E)-(2-hydroxyphenyl)methylidene]amino}ethyl)imino]methyl}phenol (MA), was derived from ethylenediamine and salicylaldehyde followed by complexation with copper (II) (MA-Cu). The chemical structures of Schiff base ligand (MA) and its complex (MA-Cu) were corroborated by means of elemental analyses, molar conductance and spectro-analytical data (1HNMR, FT-IR, FAB-MS). The conductivity data of the complex (MA-Cu) suggested non-electrolytic nature. The electronic spectra and magnetic moment value confirmed octahedral geometry of the complex. The complex (MA-Cu) showed potent urease inhibitory activity, using thiourea as standard reference.
Journal of environmental biology / Academy of Environmental Biology, India
Development of an inhibitive enzyme assay for copper2009 •
In this work the development of an inhibitive assay for copper using the molybdenum-reducing enzyme assay is presented. The enzyme is assayed using 12-molybdophosphoric acid at pH 5.0 as an electron acceptor substrate and NADH as the electron donor substrate. The enzyme converts the yellowish solution into a deep blue solution. The assay is based on the ability of copper to inhibit the molybdenum-reducing enzyme from the molybdate-reducing Serratia sp. Strain DRY5. Other heavy metals tested did not inhibit the enzyme at 10 mg l(-1). The best model with high regression coefficient to measure copper inhibition is one-phase binding. The calculated IC50 (concentration causing 50% inhibition) is 0.099 mg l(-1) and the regression coefficient is 0.98. The comparative LC50, EC50 and IC50 data for copper in different toxicity tests show that the IC50 value for copper in this study is lower than those for immobilized urease, bromelain, Rainbow trout, R. meliloti, Baker's Yeast dehydrogena...
2016 •
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