Catalytic characteristics of plant-esterase from wheat flour

Abstract

A plant-esterase extracted from wheat flour and purified with a PEG1000/NaH(2)PO(4) aqueous two-phase system was characterized for its catalytic characteristics. The optimal condition for plant-esterase to catalyze 1-naphthyl acetate was at 30°C, pH 6.5. It kept stability at 20°C during 120 min and at pH 5.5 during 60 h. The effects of metal ions, chemical modification reagents and pesticides on plant-esterase activity were investigated. It was found that Ba(2+) and Pb(2+) at concentrations of 20 mM significantly inhibited the activity of plant-esterase while Mg(2+), Ca(2+) and Fe(2+) at the same concentration enhanced the enzyme activity. Chemical modification reagents significantly influenced the activity of plant-esterase. Particularly, PMSF (4.5 mM) and N-bromosuccinimide (11 mM) inhibited by 5.40-19.87% of the enzyme activity. It is implied that serine and tryptophan are related to the enzyme activity. Plant-esterase were displayed concentration-dependent inhibition by dichlorvos, carbofuran and carbendazim (IC50 = 0.31-63.12 ppm). All these results indicated that catalytic efficiency of plant-esterase strongly depends on reaction conditions, activity effectors and amino acid residues at the active site. It makes meaningful guidance on further design of sensing material in monitoring pesticides.

Highly Sensitive Detection of Chemically Modified Thio-Organophosphates by an Enzymatic Biosensing Device: An Automated Robotic Approach

“…In particular, only 9.3 ± 1.9% of the EST2 activity was inhibited by 30 µM NBS (Supplementary Figure S1), corresponding to the final amount of oxidant in the inhibition assay of NBS-oxidized pesticides. These results are in agreement with data obtained with other esterase activities [31]. To avoid deviancy in results, all the measurements were carried out using a reference enzymatic activity of EST2 in both normal and oxidative (with addition of NBS) conditions.…”

Revisiting Jatropha curcas Monomeric Esterase: A Dienelactone Hydrolase Compatible with the Electrostatic Catapult Model

“…Moreover, EDTA positively affected esterase activity, indicating that divalent cations inhibit J. curcas DLH, as supported by our other assays with different ions. Similar effects were also observed for other plant esterases/lipases such as C. pepo [39], Glycine max, Oryza sativa [42], and those in wheat flour [43]. Metal ions can affect esterases/lipases and other α/β hydrolases activity by different mechanisms such as by coordinating with active site residues [44], overall structure alteration by allosteric regulation [44,45], surface potential alteration (a pH-dependent event) [46], and reaction equilibrium dislocation through low-soluble salt production with one of the hydrolysis reaction products, namely the carboxylic acid (mainly described for Ca 2+ [47]).…”

An Overview on the Mechanisms and Applications of Enzyme Inhibition-Based Methods for Determination of Organophosphate and Carbamate Pesticides

“…The LODs obtained for methamidophos and phoxim with purified esterase were lower than the maximum residue limits (MRLs) for these OPs in food. According to Hou et al, 142 the catalytic characteristics of a plant esterase extracted from wheat flour and purified with a PEG1000/NaH 2 PO 4 aqueous two-phase system were reported. The results showed that the chemical modification significantly influenced the activity of plant esterase.…”