Anticholinesterase insecticide retrospective.

Area of Science:

• Agricultural Entomology
• Toxicology
• Insecticide Chemistry

Background:

• Organophosphorus (OP) and methylcarbamate (MC) insecticides are anticholinesterase (antiChE) agents widely used for plant protection for 70 years.
• Approximately 90 OP and MC compounds are currently in use, representing the largest class of insecticides by number.
• These insecticides function by inhibiting acetylcholinesterase (AChE), leading to acetylcholine accumulation and subsequent excitation and death in insects and mammals.

Observation:

• Insect AChE is primarily centrally located and structurally distinct from mammalian AChE, influencing species selectivity.
• Insect populations have developed resistance to OPs and MCs through modifications in AChE, altering inhibitor specificity.
• The efficacy of antiChE insecticides relies on a balance of bioactivation and detoxification pathways involving enzymes like CYP450s, hydrolases, and glutathione S-transferases.

Findings:

• Despite a market share decline to 19%, OPs and MCs are still significant in pest management.
• Resistance, lack of new compounds, human toxicity, and patent expirations have contributed to their reduced market presence.
• Knowledge of insect AChE structure and metabolism offers potential for redesigning existing inhibitors and targeting novel sites.

Implications:

• Redesigned antiChE insecticides could overcome resistance in pest populations.
• Targeting new sites within the insect cholinergic system may offer novel pest control strategies.
• Further research into OP and MC mechanisms could revitalize their role in integrated pest management.