Characterization, Mechanism, and Application of Dipeptidyl Peptidase III: An Aflatoxin B1-Degrading Enzyme from Aspergillus terreus HNGD-TM15

Aflatoxin B₁ is a notorious mycotoxin with mutagenicity and carcinogenicity, posing a serious hazard to human and animal health. In this study, an AFB₁-degrading dipeptidyl-peptidase III mining from Aspergillus terreus HNGD-TM15 (ADPP III) with a molecular weight of 79 kDa was identified. ADPP III exhibited optimal activity toward AFB₁ at 40 °C and pH 7.0, maintaining over 80% relative activity at 80 °C. The key amino acid residues that affected enzyme activity were identified as H450, E451, H455, and E509 via bioinformatic analysis and site-directed mutagenesis. The degradation product of ADPP III toward AFB₁ was verified to be AFD_1. The zebrafish hepatotoxicity assay verified the toxicity of the AFB₁ degradation product was significantly weaker than that of AFB₁. The result of this study proved that ADPP III presented a promising prospect for industrial application in food and feed detoxification.