Study On Stereoselective Inhibition Of Enzyme With Chiral Organophosphorus Pesticides

Organophosphorus pesticides (OPs) are widely used as commercial chemicals in agriculture,for its high efficiency, high toxicity to pests and rapid degradation. Several researches reportchiral OPs have enantioselective metabolism in vivo and environments，and on the basis of theseresearches, the study on stereoselective inhibition of enzyme with chiral OPs is significant.Cellulose-and amylose-based chiral stationary phases (CSP) to comparatively separatecrufomate enantiomers on reverse-phase and normal-phase high performance liquidchromatography (RP-HPLC and NP-HPLC) are studied in this essay. The baseline separationswere obtained on Phenomenox Lux Cellulose-1, Lux Cellulose-2, and Lux Amylose-2with2-propanol/hexane, and on Lux Cellulose-1and Lux Amylose-2with acetonitrile/water asmobile phase. The results of optical rotation detections showed that (+)-enantiomer of crufomatewas firstly eluted on Lux Cellulose-1and Lux Amylose-2both on NP-HPLC and RP-HPLC,while the (-)-enantiomer was firstly eluted on Lux Cellulose-2and Lux Cellulose-3on NP-HPLC.The influences of column temperature from5°C to40°C on separation were investigated onthree CSPs. The thermodynamic parameters were calculated using Van’t Hoff equations to studythe enthalpy-driven and entropy-driven process.Meanwhile, this study includes the enantioselective inhibition kinetics of crufomate withacetylcholinesterase (ATchE) from electric eel. The inhibition rate constants (ki),Michaelis-Menten parameter (Km) and concentration of the inhibitor giving50%inhibition underdefined conditions (IC50) of the racemate and two enantiomers of crufomate were respectivelycalculated. These parameters show that different inhibition of the enantiomers and racemate ofcrufomate to ATchE, which are the basis of the future studies on the enantioselective mechanismsof chiral pesticides.