title: Catalytic profile of Arabidopsis peroxidases, AtPrx-2, 25 and 71, contributing to stem lignification.
abstract: Lignins are aromatic heteropolymers that arise from oxidative coupling of lignin precursors, including lignin monomers (p-coumaryl, coniferyl, and sinapyl alcohols), oligomers, and polymers. Whereas plant peroxidases have been shown to catalyze oxidative coupling of monolignols, the oxidation activity of well-studied plant peroxidases, such as horseradish peroxidase C (HRP-C) and AtPrx53, are quite low for sinapyl alcohol. This characteristic difference has led to controversy regarding the oxidation mechanism of sinapyl alcohol and lignin oligomers and polymers by plant peroxidases. The present study explored the oxidation activities of three plant peroxidases, AtPrx2, AtPrx25, and AtPrx71, which have been already shown to be involved in lignification in the Arabidopsis stem. Recombinant proteins of these peroxidases (rAtPrxs) were produced in Escherichia coli as inclusion bodies and successfully refolded to yield their active forms. rAtPrx2, rAtPrx25, and rAtPrx71 were found to oxidize two syringyl compounds (2,6-dimethoxyphenol and syringaldazine), which were employed here as model monolignol compounds, with higher specific activities than HRP-C and rAtPrx53. Interestingly, rAtPrx2 and rAtPrx71 oxidized syringyl compounds more efficiently than guaiacol. Moreover, assays with ferrocytochrome c as a substrate showed that AtPrx2, AtPrx25, and AtPrx71 possessed the ability to oxidize large molecules. This characteristic may originate in a protein radical. These results suggest that the plant peroxidases responsible for lignin polymerization are able to directly oxidize all lignin precursors.
authors.affiliation: Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Shigeto
authors.affiliation: Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Nagano
authors.affiliation: Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Fujita
authors.affiliation: Faculty of Agriculture, Kyushu University, Fukuoka, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tsutsumi
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000302:isolation & purification; D055162:Biocatalysis; D020134:Catalytic Domain; D045304:Cytochromes c / Q000737:chemistry; D006139:Guaiacol / Q000737:chemistry; D006835:Hydrazones / Q000737:chemistry; D008031:Lignin / Q000096:biosynthesis*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry* / Q000302:isolation & purification; D018547:Plant Stems / Q000201:enzymology*; D058849:Protein Refolding; D011748:Pyrogallol / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D029681:Arabidopsis Proteins; D006835:Hydrazones; D011748:Pyrogallol; C009370:syringaldazine; C010120:pyrogallol 1,3-dimethyl ether; D006139:Guaiacol; D008031:Lignin; D045304:Cytochromes c; D010544:Peroxidases; C000597915:Prx2 protein, Arabidopsis; C000597914:Prx25 protein, Arabidopsis; C000597916:Prx71 protein, Arabidopsis