Identification of a Novel Dihydroneopterin Aldolase as a Key Enzyme for Patulin Biodegradation in Lactiplantibacillus plantarum 6076

Patulin (PAT) is a fatal mycotoxin that exerts serious threats to human and animal health. Biodegradation of PAT is considered to be one of the promising ways for controlling its contamination. In this study, Lactiplantibacillus plantarum 6076 (LP 6076) with reliable removal efficiency on PAT was screened out from three lactic acid bacteria (LAB) strains. It was found that the PAT was eliminated through degradation by LP 6076, and the intracellular proteins played a crucial role in PAT degradation with the induction of PAT. The proteomic analysis showed that the response of LP 6076 to PAT was by a concerted effort to repair DNA damage, in parallel to adaptive changes in cell wall biosynthesis and central metabolism. Eleven differentially expressed proteins with high fold changes were picked out and identified as PAT degradation candidate enzymes. The 3D structures of the candidate enzymes were predicted, and molecular docking between the enzymes and PAT was performed. Five enzymes, including Acetoin utilization AcuB protein (AU), GHKL domain-containing protein (GHLK), Dihydroneopterin aldolase (DA), YdeI/OmpD-associated family protein (YDEL), and Transcription regulator protein (TR), could dock with PAT with lower affinity and shorter distance. Through molecular docking analysis, DA was ultimately identified as a potential key degrading enzyme. The choice of DA was substantiated by its superior combination of strong binding affinity and a productive binding pose with PAT. VAL84 and GLN51 residues of DA were likely the active sites, forming four hydrogen bonds with PAT. Our study could accelerate the commercial application of biodegradation toward PAT decontamination.