Research Progress on the Characterization, Evolution and Functions of Molluscan Peroxiredoxins.

Peroxiredoxins (Prxs) are widely distributed thiol-dependent antioxidant enzymes that contribute to cellular redox homeostasis by reducing hydrogen peroxide, organic hydroperoxides, and peroxynitrite. Studies of molluscan Prxs remain relatively limited and are concentrated mainly in Bivalvia and Gastropoda, with Prx1, Prx2, Prx4, Prx5, and Prx6 currently reported. Notably, re-examination of the sequence previously designated AwPrx4A indicates that it is more consistent with a TXNL4/DIM1-family thioredoxin-like protein than with a member of the Prx family. This review summarizes current knowledge of the sequence characteristics, phylogenetic relationships, tissue-expression patterns, and biological responses of molluscan Prxs. Available evidence supports conserved peroxide-reducing and oxidative-protective activities for several recombinant Prxs, whereas pathogen- and environmental-stress studies are dominated by transcriptional responses whose direction and magnitude vary among species, tissues, Prx subtypes, and experimental conditions. Emerging pathway-level evidence, such as Nrf2/ARE-mediated regulation of CpPrx5, has begun to clarify upstream control of Prx transcription, but direct in vivo evidence linking Prx activity to pathogen resistance, stress tolerance, or other physiological outcomes remains scarce. Future studies should expand taxonomic coverage and combine Prx-specific functional manipulation with pathway analysis and physiological phenotyping to clarify both canonical antioxidant functions and potential noncanonical roles in molluscan biology.