title: Biochemical characterization of two differentially expressed polyphenol oxidases from hybrid poplar.
abstract: Two polyphenol oxidase isoforms with distinct expression patterns were identified in hybrid poplar (Populus trichocarpaxP. deltoides). PPO-1, corresponding to the previously cloned PtdPPO (Constabel et al., Plant Physiol. 124: 285-295) was primarily leaf tissue-specific and detected only after wounding. PPO-2 was expressed constitutively in all tissue types tested except mature leaves, with highest expression in very young leaves and conducting tissues such as roots, stems and petioles. These two PPO isoforms were partially purified from hybrid poplar by ammonium sulfate fractionation followed by hydrophobic interaction chromatography. They were found to differ in stability, pH optimum, and activation by SDS. Tests with common phenolic substrates showed that PPO-1 had a broader substrate specificity than PPO-2. The distinct enzymatic properties and expression patterns of these two PPO isoforms suggest that they may have different physiological functions in hybrid poplar.
authors.affiliation: Center for Forest Biology and Department of Biology, University of Victoria, Victoria, Canada V8W3N5.
authors.forename: Jiehua
authors.initials: J
authors.lastname: Wang
authors.forename: C Peter
authors.initials: CP
authors.lastname: Constabel
mesh_terms: D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D018506:Gene Expression Regulation, Plant; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D010636:Phenols / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013379:Substrate Specificity; D014018:Tissue Distribution
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010636:Phenols; D011994:Recombinant Proteins; D012967:Sodium Dodecyl Sulfate; D004156:Catechol Oxidase