A Superefficient Ochratoxin A Hydrolase with Promising Potential for Industrial Applications

As the most seriously controlled mycotoxin produced by Aspergillus spp. and Penicillium spp., ochratoxin A (OTA) results in various toxicological effects and widely contaminates agro-products. Biological detoxification is the highest priority regarding OTA in food and feed industry, but currently available detoxification enzymes have relatively low effectiveness in terms of time and cost. Here we show a superefficient enzyme, ADH3, identified from Stenotrophomonas acidaminiphila that has a strong ability to transform OTA into nontoxic ochratoxin-α by acting as an amidohydrolase. Recombinant ADH3 (1.2 μg/mL) completely degrades 50 μg/L OTA within 90 s, while the other most efficient OTA hydrolases available take several hours. The kinetic constant showed that rADH3 (Kcat/Km) catalytic efficiency was 56.7 to 35,000 times higher than those of previous hydrolases rAfOTase, rOTase, and commercial carboxypeptidase A (CPA). Protein structure-based assay suggested that ADH3 has a preference for hydrophobic residues to form a larger hydrophobic area than other detoxifying enzymes at the cavity of the catalytic sites, and this structure allows OTA easier access to the catalytic sites. In addition, ADH3 shows considerable temperature adaptability to exert hydrolytic function at the temperature down to 0°C or up to 70°C. Collectively, we report a superefficient OTA detoxifying enzyme with promising potential for industrial applications. IMPORTANCE Ochratoxin A (OTA) can result in various toxicological effects and widely contaminates agro-products and feedstuffs. OTA detoxifications by microbial strains and bio-enzymes are significant to food safety. Although previous studies showed OTA could be transformed through several pathways, the ochratoxin-α pathway is recognized as the most effective one. However, the most currently available enzymes are not efficient enough. Here, a superefficient hydrolase, ADH3, which can completely transform 50 μg/L OTA into ochratoxin-α within 90 s was screened and characterized. The hydrolase ADH3 shows considerable temperature adaptability (0 to 70°C) to exert the hydrolytic function. Findings of this study supplied an efficient OTA detoxifying enzyme and predicted the superefficient degradation mechanism, laying a foundation for future industrial applications.