Identification and functional characterization of a novel thioredoxin MpTRX1 from Metschnikowia persimmonesis.

Thioredoxins (TRXs) are small, conserved redox-active proteins that play central roles in oxidative stress responses. Here, we identified and functionally characterized a novel thioredoxin, MpTRX1, from the newly isolated yeast Metschnikowia persimmonesis. The full-length MpTRX1 gene was cloned and expressed in Escherichia coli and Saccharomyces cerevisiae to analyze its biochemical and physiological functions. MpTRX1 encodes a 103-amino-acid protein containing a canonical CXXC redox motif, and structural modeling confirmed a conserved thioredoxin fold. Recombinant MpTRX1 exhibited clear disulfide reductase activity in both DTNB (5,5'-dithiobis-(2-nitrobenzoic acid)) and insulin reduction assays. Mutation of either catalytic cysteine residue abolished activity, confirming their essential roles. Moreover, heterologous expression of MpTRX1 in S. cerevisiae enhanced tolerance to hydrogen-peroxide-induced oxidative stress. Although the functional assays were conducted in a heterologous system, these findings demonstrate that MpTRX1 is a bona fide thioredoxin that may contribute to oxidative stress protection in M. persimmonesis. This work provides the first molecular characterization of a protein from M. persimmonesis and establishes a foundation for future studies on its potential ecological and biotechnological applications. KEY POINTS: • Identification of MpTRX1, a novel thioredoxin from M. persimmonesis. • Recombinant MpTRX1 reduces both chemical and protein substrates. • Overexpression of MpTRX1 enhances oxidative stress tolerance in S. cerevisiae.