Chicken CYP1A5 is able to hydroxylate aflatoxin B1 to aflatoxin M1.

Aflatoxin B 1 (AFB 1), a naturally-occurring mycotoxin, can cause severe toxicological and carcinogenic effects in livestock and humans. Given that the chicken is one of the most important food-producing animals, knowledge regarding AFB 1 metabolism and enzymes responsible for AFB 1 transformation in the chicken has important implications for chicken production and food safety. Previously, we have successfully expressed chicken CYP1A5 and CYP3A37 monooxygenases in E. coli , and reconstituted them into a functional CYP system consisting of CYP1A5 or CYP3A37, CPR and cytochrome b 5. In this study, we aimed to investigate the roles of CYP1A5 and CYP3A37 in the bioconversion of AFB 1 to AFM 1. Our results showed that chicken CYP1A5 was able to hydroxylate AFB 1 to AFM 1. The formation of AFM 1 followed the typical Michaelis–Menten kinetics. The kinetics parameters of V max and K m were determined as 0.83 ± 0.039 nmol/min/nmol P450 and 26.9 ± 4.52 μM respectively. Docking simulations further revealed that AFB 1 adopts a "side-on" conformation in chicken CYP1A5, facilitating the hydroxylation of the C9a atom and the production of AFM 1. On the other hand, AFB 1 assumes a "face-on" conformation in chicken CYP3A37, leading to the displacement of the C9a atom from the heme iron and explaining the lack of AFM 1 hydroxylation activity. The results demonstrate that chicken CYP1A5 possesses efficient hydroxylase activity towards AFB 1 to form AFM 1. [Display omitted] • E. coli expressed chicken CYP1A5 is able to hydroxylate aflatoxin B 1 to aflatoxin M 1. • The formation of aflatoxin M 1 followed typical Michaelis–Menten kinetics. • Chicken CYP1A5 is an efficient enzyme catalyzing aflatoxin B 1 hydroxylation. • AFB 1 adopts a "side-on" conformation in chicken CYP1A5, facilitating the hydroxylation of the C9a atom. [ABSTRACT FROM AUTHOR]