Patulin Detoxification by Evolutionarily Divergent Reductases of Gluconobacter oxydans ATCC 621

The mycotoxin patulin in processed apple juice poses a significant threat to food safety, driving the need for effective detoxification strategies. Gluconobacter oxydans ATCC 621 can detoxify patulin to ascladiol using either the short-chain dehydrogenases/reductases (SDRs)─GOX0525, GOX1899, and GOX0716─or the aldo-keto reductase (AKR) GOX1462. While GOX0525 and GOX1899 have been previously characterized, this study focuses on GOX0716 and GOX1462, evaluating their optimal pH, thermostability, thermoactivity, and substrate specificity, thereby completing the characterization of all four reductases. GOX0716 and GOX1462 exhibit pH optima of 6 and 7, respectively, and are functional across a broad temperature range of 25-55 °C. GOX0716 was determined to be more thermostable than GOX1462, with a half-life of 4.95 h at 55 °C. Phylogenetic analysis revealed that these SDRs belong to distinct evolutionary families with broad substrate specificity. GOX0716 is a member of the SDR79 family, which shares a common ancestry with the SDR111 family of fungal anthrol reductases. Conversely, GOX1462 is a member of the AKR18 family, which is involved in detoxification of the mycotoxin, deoxynivalenol (DON). Molecular docking analysis of Alphafold models highlights distinct variations in the active site architectures of these SDRs and AKRs, offering insights into their differing catalytic efficiencies toward patulin.