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Characterization of an ascorbate peroxidase in plastids of tobacco BY‐2 cells
Author(s) -
Madhusudhan Rapolu,
Ishikawa Takahiro,
Sawa Yoshihiro,
Shigeoka Shigeru,
Shibata Hitoshi
Publication year - 2003
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2003.00066.x
Subject(s) - apx , plastid , biochemistry , chloroplast , peroxidase , biology , ascorbic acid , spinach , thylakoid , enzyme , gene , food science
In higher plants, ascorbate peroxidase (APX; EC 1.11.1.11), the major H 2 O 2 ‐scavenging enzyme, occurs in several distinct isoenzymes that are localized in cytosol and various cell organelles. Here, we have purified and characterized an APX from the soluble fraction of plastids of non‐photosynthetic tobacco BY‐2 cells. The plastidic APX was a monomer with a molecular weight of 34 000. The enzymatic properties of the plastidic APX, including the rapid inactivation by H 2 O 2 in ascorbate‐depleted medium, were highly comparable with those of the chloroplastic stromal APX of spinach and tea leaves. However, the other chloroplastic APX isoenzyme, the thylakoid‐membrane bound APX, was not detected in the plastids of the BY‐2 cells. The N‐terminal amino acid sequence of the plastidic APX was completely identical with the deduced amino acid sequence of a previously identified cDNA sequence of tobacco chloroplastic APX. When a green fluorescence protein gene tagged with the chloroplast‐targeting signal sequence of APX was expressed in the BY‐2 cells, the fluorescence protein exclusively localized into plastids, and not into mitochondria. We conclude that plastidic APX in non‐photosynthetic tissues is the same as the chloroplastic APX that occurs in leaves.