The interaction mechanisms of catalase (CAT) with pesticides (including organophosphates: disulfoton, isofenphos-methyl, malathion, isocarbophos, dimethoate, dipterex, methamidophos and acephate; carbamates: carbaryl and methomyl; pyrethroids: fenvalerate and deltamethrin) were first investigated by flow injection (FI) chemiluminescence (CL) analysis and molecular docking. By homemade FI-CL model of lg[(I0-I)/I]=lgK+nlg[D], it was found that the binding processes of pesticides to CAT were spontaneous with the apparent binding constants K of 10(3)-10(5) L mol(-1) and the numbers of binding sites about 1.0. The binding abilities of pesticides to CAT followed the order: fenvalerate>deltamethrin>disulfoton>isofenphos-methyl>carbaryl>malathion>isocarbophos>dimethoate>dipterex>acephate>methomyl>methamidophos, which was generally similar to the order of determination sensitivity of pesticides. The thermodynamic parameters revealed that CAT bound with hydrophobic pesticides by hydrophobic interaction force, and with hydrophilic pesticides by hydrogen bond and van der Waals force. The pesticides to CAT molecular docking study showed that pesticides could enter into the cavity locating among the four subdomains of CAT, giving the specific amino acid residues and hydrogen bonds involved in CAT-pesticides interaction. It was also found that the lgK values of pesticides to CAT increased regularly with increasing lgP, Mr, MR and MV, suggesting that the hydrophobicity and steric property of pesticide played essential roles in its binding to CAT.
Keywords: Catalase; Flow injection chemiluminescence; Interaction mechanism; Molecular docking; Pesticides.
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