Evaluation of a robust engineered enzyme towards organophosphorus insecticide bioremediation using planarians as biosensors

A supramolecular catalyst based on sodium alginate and viologen calix[4]resorcinol for the room temperature hydrolysis of paraoxon

Properties of paraoxon, such as poor water solubility, low rate of natural decomposition, ability to accumulate in soil and wastewater, lead to the fact that paraoxon is found in various agricultural products and textiles. In this regard, the search for effective ways of paraoxon degradation becomes an extremely urgent problem, which can be solved by creating catalysts by mimicking paraxonase. In this work, a complex of physicochemical methods was used to study the supramolecular interactions of sodium alginate, which has a calcium-binding ability similar to paraxonase, with viologen calix[4]resorcinol and to reveal the nature of the intermolecular interactions between them resulting in the spontaneous formation of nanoparticles. Before proceeding to the investigation of the binding ability of obtained nanoparticles to paraoxon, the encapsulating effect of nanoparticles on a number of model substrates of different solubility (doxorubicin hydrochloride, quercetin and oleic acid) was studied. The kinetics of paraoxon hydrolysis reaction using these nanoparticles was studied at room temperature in an aqueous medium by spectrophotometric method. The rate of this reaction increases with increasing concentration of stable nanoparticles having hydrophobic domains that ensure paraoxon immobilization. The results obtained allow considering the supramolecular polysaccharide/calixarene system as an effective biomimetic catalyst.

Tuning the Envelope Structure of Enzyme Nanoreactors for In Vivo Detoxification of Organophosphates

Encapsulated phosphotriesterase nanoreactors show their efficacy in the prophylaxis and post-exposure treatment of poisoning by paraoxon. A new enzyme nanoreactor (E-nRs) containing an evolved multiple mutant (L72C/Y97F/Y99F/W263V/I280T) of Saccharolobus solfataricus phosphotriesterase (PTE) for in vivo detoxification of organophosphorous compounds (OP) was made. A comparison of nanoreactors made of three- and di-block copolymers was carried out. Two types of morphology nanoreactors made of di-block copolymers were prepared and characterized as spherical micelles and polymersomes with sizes of 40 nm and 100 nm, respectively. The polymer concentrations were varied from 0.1 to 0.5% (w/w) and enzyme concentrations were varied from 2.5 to 12.5 μM. In vivo experiments using E-nRs of diameter 106 nm, polydispersity 0.17, zeta-potential -8.3 mV, and loading capacity 15% showed that the detoxification efficacy against paraoxon was improved: the LD50 shift was 23.7xLD50 for prophylaxis and 8xLD50 for post-exposure treatment without behavioral alteration or functional physiological changes up to one month after injection. The pharmacokinetic profiles of i.v.-injected E-nRs made of three- and di-block copolymers were similar to the profiles of the injected free enzyme, suggesting partial enzyme encapsulation. Indeed, ELISA and Western blot analyses showed that animals developed an immune response against the enzyme. However, animals that received several injections did not develop iatrogenic symptoms.

A systematic review on the implementation of advanced and evolutionary biotechnological tools for efficient bioremediation of organophosphorus pesticides

Ever since the concept of bioremediation was introduced, microorganisms, microbial enzymes and plants have been used as principal elements for Organophosphate pesticide (OPP) bioremediation. The enzyme systems and genetic profile of these microbes have been studied deeply in past years. Plant growth promoting rhizobacteria (PGPR) are considered as one of the potential candidates for OPP bioremediation and has been widely used to stimulate the phytoremediation potential of plants. Constructed wetlands (CWs) in OPP biodegradation have brought new prospects to microcosm and mesocosm based remediation strategies. Application of synthetic biology has provided a new dimension to the field of OPP bioremediation by introducing concepts like, gene manipulation andediting, expression and regulation of catabolic enzymes, implementation of whole-cell based and enzyme based biosensor systems for the detection and monitoring of OPP pollution in both terrestrial and aquatic environment. System biology and bioinformatics tools have rendered significant knowledge regarding the genetic, enzymatic and biochemical aspects of microbes and plants thereby, helping researchers to analyze the mechanism of OPP biodegradation. Structural biology has provided significant conceptual information regarding OPP biodegradation pathways, structural and functional characterization of metabolites and enzymes, enzyme-pollutant interactions, etc. Therefore, this review discussed the prospects and challenges of most advanced and high throughput strategies implemented for OPP biodegradation. The review also established a comparative analysis of various bioremediation techniques and highlighted the interdependency among them. The review highly suggested the simultaneous implementation of more than one remediation strategy or a combinational approach creating an advantageous hybrid technique for OPP bioremediation.

Enzyme Nanoreactor for In Vivo Detoxification of Organophosphates

A nanoreactor containing an evolved mutant of Saccharolobus solfataricus phosphotriesterase (L72C/Y97F/Y99F/W263V/I280T) as a catalytic bioscavenger was made for detoxification of organophosphates. This nanoreactor intended for treatment of organophosphate poisoning was studied against paraoxon (POX). Nanoreactors were low polydispersity polymersomes containing a high concentration of enzyme (20 μM). The polyethylene glycol-polypropylene sulfide membrane allowed for penetration of POX and exit of hydrolysis products. In vitro simulations under second order conditions showed that 1 μM enzyme inactivates 5 μM POX in less than 10 s. LD₅₀-shift experiments of POX-challenged mice through intraperitoneal (i.p.) and subcutaneous (s.c.) injections showed that intravenous administration of nanoreactors (1.6 nmol enzyme) protected against 7 × LD₅₀ i.p. in prophylaxis and 3.3 × LD₅₀ i.p. in post-exposure treatment. For mice s.c.-challenged, LD₅₀ shifts were more pronounced: 16.6 × LD₅₀ in prophylaxis and 9.8 × LD₅₀ in post-exposure treatment. Rotarod tests showed that transitory impaired neuromuscular functions of challenged mice were restored the day of experiments. No deterioration was observed in the following days and weeks. The high therapeutic index provided by prophylactic administration of enzyme nanoreactors suggests that no other drugs are needed for protection against acute POX toxicity. For post-exposure treatment, co-administration of classical drugs would certainly have beneficial effects against transient incapacitation.

Enzyme engineering and its industrial applications

Recently, there has been an increase in the demand for enzymes with modified activity, specificity, and stability. Enzyme engineering is an important tool to meet the demand for enzymes adjusted to different industrial processes. Knowledge of the structure and function of enzymes guides the choice of the best strategy for engineering enzymes. Each enzyme engineering strategy, such as rational design, directed evolution, and semi-rational design, has specific applications, as well as limitations, which must be considered when choosing a suitable strategy. Engineered enzymes can be optimized for different industrial applications by choosing the appropriate strategy. This review features engineered enzymes that have been applied in food, animal feed, pharmaceuticals, medical applications, bioremediation, biofuels, and detergents.

Enzymatic decontamination of paraoxon-ethyl limits long-term effects in planarians

Organophosphorus compounds (OP) are highly toxic molecules used as insecticides that inhibit cholinesterase enzymes involved in neuronal transmission. The intensive use of OP for vector control and agriculture has led to environmental pollutions responsible for severe intoxications and putative long-term effects on humans and wild animals. Many in vivo models were studied over the years to assess OP acute toxicity, but the long-term effects are poorly documented. Planarian, a freshwater flatworm having a cholinergic system, has emerged as a new original model for addressing both toxicity and developmental perturbations. We used Schmidtea mediterranea planarians to evaluate long-term effects of paraoxon-ethyl at two sublethal concentrations over three generations. Toxicity, developmental perturbations and disruption of behavior were rapidly observed and higher sensitivity to paraoxon-ethyl of next generations was noticed suggesting that low insecticide doses can induce transgenerational effects. With the view of limiting OP poisoning, SsoPox, an hyperthermostable enzyme issued from the archaea Saccharolobus solfataricus, was used to degrade paraoxon-ethyl prior to planarian exposure. The degradation products, although not lethal to the worms, were found to decrease cholinesterase activities for the last generation of planarians and to induce abnormalities albeit in lower proportion than insecticides.

[Organophosphorus poisoning: Towards enzymatic treatments]

Organophosphorus compounds (OP) are toxic molecules developed as insecticides and chemical warfare nerve agents (CWNAs). Most OP are neurotoxic and act as nervous system disruptors by blocking cholinergic transmission. They are therefore responsible for many poisonings worldwide. OP toxicity may result either from acute or chronic exposure, and their poisoning effect were evaluated using several animal models. These latter were also used for evaluating the efficacy of antidotes. Strategies based on enzymes that can trap (stoichiometric bioscavengers) or degrade (catalytic bioscavengers) OP, were particularly studied since they allow effective decontamination, without toxicity or environmental impact. This review summarizes the results obtained in vivo with enzymes through three levels: prophylaxis, treatment and external decontamination. The efficiency of enzymatic treatments in different animal models is presented and the relevance of these models is also discussed for a better extrapolation to humans.