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 microM) of deltamethrin with alpha-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 microM. The larvicidal bioassay tests indicated that the mixture from the degradation reaction showed LC(50) increased significantly (P<0.05). This is the first report demonstrating deltamethrin metabolism by chymotrypsin.