Purification,Biochemical Properties and Insecticides Susceptibility of Acetylcholinerase from Housefly(Musca domestica L.)

Acethlcholinesterase (AChE, EC3.1.1.7)is an important enzyme sources in enzyme-based methods for pesticide instant determi- nation. In this study, 3-carboxyphenyl ethydimethyl ammonium(CEA)method was adopted to purify AChE from housefly(Musca domestica). The effects of reaction temperature,pH,ATChI concentration,and DTNB concentration on the purified and crude AChE activities were in- vestigated. Also, the inhibitory effects of different insecticides on the purified and crude AChE activities were measured. The results showed that AChE purification fold can be reached to 672.36 when the yield was 34.68%. Significantly highest purified AChE activity was observed when the experiment conditions were 35 ℃,pH7.2,2 500 μmol·L-1 ATChI and 0.2 mol·L-1 DTNB. In addition, significantly highest crude AChE enzyme activities were observed at 35 ℃,pH7.8,1 500 μmol·L-1 ATChI,0.4 mol·L-1 DTNB. The IC50 ratio of crude and purified AChE, caused by fenobucarb, acephate,metolcarb,methamidophos,chlorpyrifos,carbofuran,pirimicarb,methomyl,phoxim were more than 6. The IC50 ratio were 4.826,1.184 and 0.099 caused by carbaryl, diazinon and triazophos, respectively. The results showed that purified AChE is more sensitive to tested insecticides than crude AChE, but the sensitivity may depend on chemical structure of insecticides and re- action conditions, which indicated the purified AChE-based methods for instant pesticides determination are more effective and useful at optimized conditions.