Kinetics Characteristics of Wheat Bran Esterase on Organophosphorus and Carbamate Pesticides

KeyWord:wheat bran esterase  enzyme dynamics  pesticide residue  sensitivity  organophosphorus  carbamate

Abstract:

      The enzyme kinetic constants(Ki,Ka,K2) and half inhibitory concentration(IC50) were determined to reveal the kinetic characteristics of wheat bran esterase with the index of enzyme activity inhibition rate.Results showed that,the sensitivity order of wheat bran esterase to three organophosphorus pesticides was as follows: dichlorvos£¾methyl parathion£¾dimethoate,and that to carbamate pesticides was: isoprocarb>carbaryl>carbosulfan.In addition,the corresponding IC50 values for the six pesticides were 0.176,1.754,2.583,0.489,0.799,2.035 mg/L,respectively.The conclusion that the inhibitory effects of pesticides on wheat bran esterase were selective in different degrees was obtained by comparing the kinetic constants(Ki£¬Ka£¬K2) of wheat bran esterase and IC50 values of the six pesticides.And the main reason for the difference of the sensitivity to pesticides was the affinity of wheat bran esterase and pesticides.Actually,lettuce,green beans and grapes were detected to contain pesticides by using this method,and the pesticide residues in grape were confirmed to be dimethoate.The method could provide a theoretical basis for the application of wheat bran esterase in pesticide detection.