Partial characterization of deltamethrin metabolism catalyzed by chymotrypsin

Deltamethrin degradation was assessed by measuring deltamethrin reduction with GC–MS and UV–Vis spectrophotometry following incubation of various concentrations (4.96–24.80 μM) of deltamethrin with α-chymotrypsin from bovine pancreas. The retention times of crude products of deltamethrin metabolic reactions were 37.968 min, 37.415 min, 36.490 min, and 35.895 min. The UV–Vis spectrophotometric peak absorbance of deltamethrin was at 264 nm, and the peak absorbance of deltamethrin metabolic products were at 250 nm and 296 nm, respectively. Michaelis–Menten metabolic rate constants (Vmax and Km) were calculated by nonlinear regression for chymotrypsin using GraphPad Prism 4.0, the Vmax was 97.97 ± 26.57 nmol/L/min and Km was 7.84 ± 3.83 μM. The larvicidal bioassay tests indicated that the mixture from the degradation reaction showed LC50 increased significantly (P < 0.05). This is the first report demonstrating deltamethrin metabolism by chymotrypsin.