The furofuran-ring selectivity, hydrogen peroxide-production and low Km value are the three elements for highly effective detoxification of aflatoxin oxidase

AFO (aflatoxin oxidase), an enzyme from Armillariella tabescens previously named aflatoxin detoxifizyme, exhibits oxidative detoxification activity toward aflatoxin El and sterigmatocystin. Bioinformatics reveals that AFO is a newly discovered oxidase because AFO does not share any significant similarities with any known oxidase. It is critically important to understand how AFO acts on aflatoxin B-1. In this study, in addition to aflatoxin B-1 (AFB(1)) and sterigmatocystin (ST), five other chemicals that have furan or pyran structures were investigated. The results indicated that in addition to AFB(1) and ST, AFO is also able to act on versicolorin A, 3,4-dihydro-2H-pyran and furan. These results suggested that 8,9-unsaturated carbon carbon bond of aflatoxin B-1 is the potential reactive site for AFO. Further findings indicated that the action of AFO is oxygen-dependent and hydrogen peroxide-producing. The simultaneously produced-hydrogen peroxide possibly plays the essential role in detoxification of AFO. In addition, the extremely low K-m value of 0.33 mu mol/l for AFO-AFB(1) and 0.11 mu mol/l for AFO-ST signifies that AFO is highly selective for AFB(1) as well as ST. (C) 2014 Elsevier Ltd. All rights reserved.