Cytochrome P-450 Catalyzed Insecticide Metabolism. Prediction of Regio- and Stereoselectivity in the Primer Metabolism of Carbofuran: A Theoretical Study

The molecular mechanism of carbofuran metabolism was investigated by molecular modeling using the energy-minimized active site of cytochrome P-450 cam . A feasible binding conformation of carbofuran was subjected to Monte Carlo (MC) conformational search and molecular dynamics (MD) simulation in the active site to obtain the global minimum of the enzyme−substrate complex. For exploring its conformational space, MC was found to be more effective than simple MD. Enzyme−substrate interactions were examined in detail in all low-energy states. Distances between the active ferryl oxygen of the central heme unit and the reactive centers of carbofuran involved in oxidative metabolism were monitored. H-bonding interaction between the carbamate group of carbofuran and the Tyr96-OH group, as well as the steric effects of Val247 and Val295, were found to be crucial for the orientation of carbofuran. The preferred formation of 3-hydroxycarbofuran, the major primer metabolite, could be rationalized by the model. The configuration at the C3 atom was predicted to be S in accordance with the stereospecificity reported for the natural substrate.