Recombinant Stromal APX Defective in the Unique Loop Region Showed Improved Tolerance to Hydrogen Peroxide

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Ascorbate peroxidase (APX) of chloroplasts plays a pivotal role in detoxifying the hydrogen peroxide (H₂O₂) produced through photoexcitation of the photosystem, but it easily loses its catalytic activity under attack by excess H₂O₂. Here we report that the H₂O₂-tolerance of APX localized in the stroma of chloroplasts was improved by removing a unique 16-amino-acid-residue loop not found in H₂O₂-tolerant isoforms of cytosol and glyoxysome.