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 (V_max and K_m) were calculated by nonlinear regression for chymotrypsin using GraphPad Prism 4.0, the V_max was 97.97 ± 26.57 nmol/L/min and K_m 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.