Purification, characterization, and sensitivity to pesticides of carboxylesterase from Dendrolimus superans (Lepidoptera: Lasiocampidae)

Characterization of the role of esterases in the biodegradation of organophosphate, carbamate, and pyrethroid pesticides

Ester-containing organophosphate, carbamate, and pyrethroid (OCP) pesticides are used worldwide to minimize the impact of pests and increase agricultural production. The toxicity of these chemicals to humans and other organisms has been widely reported. Chemically, these pesticides share an ester bond in their parent structures. A particular group of hydrolases, known as esterases, can catalyze the first step in ester-bond hydrolysis, and this initial regulatory metabolic reaction accelerates the degradation of OCP pesticides. Esterases can be naturally found in plants, animals, and microorganisms. Previous research on the esterase enzyme mechanisms revealed that the active sites of esterases contain serine residues that catalyze reactions via a nucleophilic attack on the substrates. In this review, we have compiled the previous research on esterases from different sources to determine and summarize the current knowledge of their properties, classifications, structures, mechanisms, and their applications in the removal of pesticides from the environment. This review will enhance the understanding of the scientific community when studying esterases and their applications for the degradation of broad-spectrum ester-containing pesticides.

Esterase is a powerful tool for the biodegradation of pyrethroid insecticides

Agricultural and household applications of pyrethroid insecticides have significantly increased residual concentrations in living cells and environments. The enhanced concentration is toxic for living beings. Pyrethroid hydrolase enzyme (pyrethroid catalyzing esterase) regulates pyrethroid degradation, and has been well reported in various organisms (bacteria, fungi, insects and animals). Hydrolysis mechanisms of these esterases are different from others and properly function at factors viz., optimum temperature, pH and physicochemical environment. Active site of the enzyme contains common amino acids that play important role in pyrethroid catalysis. Immobilization technology emphasizes the development of better reusable efficiency of pyrethroid hydrolases to carry out large-scale applications for complete degradation of pyrethroids from the environments. In this review we have attempted to provide insights of pyrethroid-degrading esterases in different living systems along with complete mechanisms.

Larvicidal activity and insecticidal mechanism of Chelidonium majus on Lymantria dispar

Based on the broad spectrum of its biological activities, Chelidonium majus has been studied extensively in the medical field. However, few studies have focused on the insecticidal activity of C. majus, and the precise mechanism of its insecticidal activity. In the present study, larvicidal activity and insecticidal mechanism of C. majus on Lymantria dispar were investigated using bioassays, in vitro and in vivo enzyme activity assays, determination of the nutritional index, and gene transcription analysis. The results showed that alkaloids are the main insecticidal ingredients in C. majus. Among the five isoquinoline alkaloids, coptisine was present at the highest concentration (1624.23mg/L), while tetrahydrocoptisine showed the lowest concentration (0.47mg/L). Both the crude extract of C. majus (CECm) and the total alkaloids of C. majus (TACm) possessed a potent insecticidal activity toward L. dispar larvae. TACm had significant effects on the relative consumption rate, efficiency of conversion of digested food into growth, approximate digestibility, and approximate digestibility of L. dispar larvae. Enzyme activity assays suggested that both CECm and TACm displayed their strongest inhibitory activity to in vitro glutathione S-transferase (GST) and acetylcholinesterase (AChE), and showed the weakest inhibition of in vitro carboxylesterase (CarE). Moreover, CECm and TACm affected the in vivo activities of five enzymes. The in vivo activities of AChE and CarE in L. dispar larvae were inhibited significantly by CECm and TACm. Additionally, qRT-PCR analysis revealed that the transcription of the five enzymes was also affected by TACm. In conclusion, alkaloids in C. majus showed a prominent toxicity to L. dispar by reducing food intake, influencing nutritional indices, and affecting the activity and mRNA transcription of detoxifying and protective enzymes. This study provides novel insights into the insecticidal mechanism of C. majus.

Transcriptome Analysis and Discovery of Genes Relevant to Development in Bradysia odoriphaga at Three Developmental Stages

Bradysia odoriphaga (Diptera: Sciaridae) is the most important pest of Chinese chive (Allium tuberosum) in Asia; however, the molecular genetics are poorly understood. To explore the molecular biological mechanism of development, Illumina sequencing and de novo assembly were performed in the third-instar, fourth-instar, and pupal B. odoriphaga. The study resulted in 16.2 Gb of clean data and 47,578 unigenes (≥125 bp) contained in 7,632,430 contigs, 46.21% of which were annotated from non-redundant protein (NR), Gene Ontology (GO), Clusters of Orthologous Groups (COG), Eukaryotic Orthologous Groups (KOG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. It was found that 19.67% of unigenes matched the homologous species mainly, including Aedes aegypti, Culex quinquefasciatus, Ceratitis capitata, and Anopheles gambiae. According to differentially expressed gene (DEG) analysis, 143, 490, and 309 DEGs were annotated as involved in the developmental process in the GO database respectively, in the comparisons of third-instar and fourth-instar larvae, third-instar larvae and pupae, and fourth-instar larvae and pupae. Twenty-five genes were closely related to these processes, including developmental process, reproduction process, and reproductive organs development and programmed cell death (PCD). The information of unigenes assembled in B. odoriphaga through transcriptome and DEG analyses could provide a detailed genetic basis and regulated information for elaborating the developmental mechanism from the larval, pre-pupal to pupal stages of B. odoriphaga.