Aflatoxin B1 (AFB1) is a highly toxic mycotoxin that threatens global food and feed safety. While enzymatic detoxification is a promising strategy, robust and efficient enzymes remain scarce. This study identified that the multicopper oxidase CueO from Escherichia coli (E. coli) CG1061 transforms AFB1 into the less toxic aflatoxin Q1, exhibiting optimal activity at pH 8 and 60 °C. The CueO-2,2'-azino-bis (3-ethylbenzothazoline-6-sulfonic acid) (ABTS) mediator system achieved >90% of AFB1 transformation in 10 min and complete transformation in 20 min, significantly outperforming CueO alone (51% in 60 min). Mechanistically, CueO oxidizes ABTS to form the ABTṠ+ radical, which subsequently oxidizes AFB1. Mutants (Met510Leu, Asp439Ala, and Pro444Ala) exhibited enhanced enzymatic activity toward ABTS but showed no improvement in the catalytic efficiency for AFB1 transformation. Molecular docking suggests this is because AFB1 binds to surface-exposed residue Ser243, distal to the active site. These findings highlight E. coli CueO's a promising candidate for managing AFB1 contamination.
Chen et al. (Wed,) studied this question.