Correction to Concurrent Cooperativity and Substrate Inhibition in the Epoxidation of Carbamazepine by Cytochrome P450 3A4 Active Site Mutants Inspired by Molecular Dynamics Simulations

The critical role of porcine cytochrome P450 3A46 in the bioactivation of aflatoxin B1

Aflatoxin B₁ (AFB₁) is bioactivated by cytochrome P450 (CYP) 3A isoforms in humans to generate the highly reactive epoxide intermediate AFB₁-8,9-epoxide (AFBO), causing hepatotoxicity and hepatocarcinoma. Due to the unavoidable contamination in their feed, pigs are more likely to be exposed to AFB₁ and indirectly harm human health. Therefore, identifying the porcine CYP3A isoforms involved in AFB₁-8,9-epoxidation is critical. In this study, we used codon optimization and N-terminal coding sequence modification to modify a CYP3A46 recombinant protein that exhibits good structure and catalytic activities and revealed its strong AFB₁-8,9-epoxidase activity for the first time. Site-directed mutagenesis, kinetics and docking analyses were performed and demonstrated that residues Phe-108, Ser-119, Phe-215, Phe-304 and Thr-309 play important roles in AFB₁-8,9-epoxidation and its responsiveness to α-naphthoflavone. Interestingly, we uncovered the dual and reverse roles of Phe-304 in CYP3A46, CYP3A5 and CYP3A4 in AFB₁ oxidation. Unlike the π-π interaction between the Phe-304 phenyl of CYP3A4 and the AFB₁ aromatic ring, Phe-304 of CYP3A46 may function to provide steric hindrance to bind AFB₁. Phe-108 and Phe-215 could stabilize AFB₁ with a potentially productive orientation through van der Waals interactions with AFB₁. Ser-119 and Thr-309 are likely to function to form H-bonds with AFB₁. This study broadens our knowledge of AFB₁ bioactivation in pigs and may contribute to reduce the deleterious effects of AFB₁ in pigs and humans.