Anionic peroxidases have been proposed to be a key enzyme for lignification in poplar. On the other hand, there are many genes encoding an anionic peroxidase in Populus trichocarpa genome, and their physiological functions are still unknown. Ampholine isoelectric focusing analysis revealed anionic peroxidases as dominant peroxidases in enzyme preparations from various organs. Using two-dimensional electrophoresis (2-DE) followed by peptide mass fingerprint (PMF) analysis, we surveyed the localization of anionic peroxidase isoenzymes in various organs of Populus alba L. Peroxidase isoenzymes were extracted from various organs and fractionated by a Concanavallin A Sepharose column. Each protein was separated by 2-DE gels and some anionic peroxidase isoenzymes in each organ were identified via PMF analysis. Transcript and protein of individual peroxidase indicate that the expression profile of each isoenzyme is quite different, for example, organspecific gene, stress-response gene, and multifunction gene, even though they are in the same cluster. These results suggest that individual anionic isoenzymes in this small cluster were differently regulated at transcription, translation, or posttranslation.
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