Identification and characterization of a novel fungal pyranose 2-oxidase from the Punctularia strigosozonata with potent cytotoxicity against pancreatic carcinoma cell lines

Pyranose oxidase (POx) is a FAD-dependent oxidoreductase that catalyzes the oxidation of D-glucose to 2-keto-D-glucose with concomitant production of hydrogen peroxide (H 2 O 2 ). Although POx has been well characterized in several fungi and bacteria, its potential in cancer therapy remains largely unexplored. In this study, we identified a novel pyranose 2-oxidase, designated PsPOx, from the wood-decaying fungus Punctularia strigosozonata through gene mining. The gene was codon-optimized, synthesized, and heterologously expressed in Escherichia coli . The recombinant enzyme was purified and biochemically characterized. Sequence alignment and structural modeling confirmed that PsPOx possesses all conserved features of the GMC superfamily. Kinetic analysis showed that PsPOx exhibits the highest catalytic efficiency ( k cat / K m = 85.09 mM -1 s -1 ) towards D-glucose, with a K m value of 0.8375 mM, indicating a strong substrate affinity. Using the CCK-8 assay, PsPOx demonstrated potent dose-dependent cytotoxicity against three human pancreatic carcinoma cell lines (PANC-1, AsPC-1, and BxPC-3), with IC50 values of 257.8, 195.2, and 176.2 ng mL -1 , respectively. However, the IC 50 value for the normal human pancreatic epithelial cell line hTERT-HPNE was 195.6 ng mL -1 , which was comparable to those for AsPC-1 and BxPC-3, indicating that free PsPOx lacks selectivity between tumor and normal cells. Mechanistic studies revealed that PsPOx treatment increased intracellular and mitochondrial reactive oxygen species (ROS) levels, induced G0/G1 cell cycle arrest, downregulated Cyclin D1 and PCNA expression, and triggered apoptosis in BxPC-3 cells. These results preliminarily demonstrate that PsPOx possesses antitumor activity in vitro and may serve as a candidate for further development.