The Experts below are selected from a list of 1941 Experts worldwide ranked by ideXlab platform
Yuji Tsutsumi - One of the best experts on this subject based on the ideXlab platform.
-
enzymatic activities for lignin monomer intermediates highlight the biosynthetic pathway of syringyl monomers in robinia pseudoacacia
Journal of Plant Research, 2017Co-Authors: Jun Shigeto, Shinya Sasaki, Yukie Ueda, Koki Fujita, Yuji TsutsumiAbstract:Most of the known 4-coumarate:coenzyme A ligase (4CL) isoforms lack CoA-ligation activity for sinapic acid. Therefore, there is some doubt as to whether sinapic acid contributes to Sinapyl Alcohol biosynthesis. In this study, we characterized the enzyme activity of a protein mixture extracted from the developing xylem of Robinia pseudoacacia. The crude protein mixture contained at least two 4CLs with sinapic acid 4-CoA ligation activity. The crude enzyme preparation displayed negligible sinapaldehyde dehydrogenase activity, but showed ferulic acid 5-hydroxylation activity and 5-hydroxyferulic acid O-methyltransferase activity; these activities were retained in the presence of competitive substrates (coniferaldehyde and 5-hydroxyconiferaldehyde, respectively). 5-Hydroxyferulic acid and sinapic acid accumulated in the developing xylem of R. pseudoacacia, suggesting, in part at least, sinapic acid is a Sinapyl Alcohol precursor in this species.
-
Catalytic profile of Arabidopsis peroxidases, AtPrx-2, 25 and 71, contributing to stem lignification
PloS one, 2014Co-Authors: Jun Shigeto, Koki Fujita, Mariko Nagano, Yuji TsutsumiAbstract: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.
-
identification of tyr74 and tyr177 as substrate oxidation sites in cationic cell wall bound peroxidase from populus alba l
FEBS Journal, 2012Co-Authors: Jun Shigeto, Yuji Tsutsumi, Yoshitaka Itoh, Ryuichiro KondoAbstract:Cationic cell wall-bound peroxidase (CWPO-C) has the capability to oxidize Sinapyl Alcohol, ferrocytochrome c, and synthetic lignin polymers, unlike most peroxidases that have been characterized in flowering plants, such as horseradish peroxidase and Arabidopsis thaliana peroxidase A2. It has been suggested that the oxidation site is located on the CWPO-C surface, and homology modeling and chemically modified CWPO-C studies suggest that Tyr74 and/or Tyr177 are possible participants in the catalytic site. The present study clarifies the importance of these Tyr residues for substrate oxidation, using recombinant CWPO-C and recombinant mutant CWPO-C with phenylalanine substitution(s) for tyrosine. Such recombinant proteins, produced in Escherichia coli as inclusion bodies, were successfully refolded to yield the active form, and purified recombinant protein solutions exhibited typical spectra of high-spin ferric protein and displayed H2O2-dependent oxidation of guaiacol, 2,6-dimethoxyphenol, and syringaldazine. Measurement of peroxidase activity with these guaiacyl and syringyl compounds as reducing substrates indicated that a single mutation, Y74F or Y177F, resulted in substantial loss of oxidation activity (∼ 40–60% and 82%, respectively). Also, over 95% of the oxidation activity was lost with a double mutation, Y74F/Y177F. These results indicated that Tyr74 and Tyr177, rather than the heme pocket, play a central role in the oxidation of these substrates. This is the first report of active residues on an enzyme surface being identified in a plant peroxidase. This study also suggests that Sinapyl Alcohol incorporation into lignin is performed by a peroxidase that generates Tyr radicals on its surface.
-
the cationic cell wall peroxidase having oxidation ability for polymeric substrate participates in the late stage of lignification of populus alba l
Plant Molecular Biology, 2006Co-Authors: Shinya Sasaki, Keiichi Baba, Tomoaki Nishida, Yuji Tsutsumi, Ryuichiro KondoAbstract:Previously we reported that purified Cell Wall Peroxidase-Cationic (CWPO-C) from poplar callus (Populus alba L.) oxidizes Sinapyl Alcohol and polymeric substrate unlike other plant peroxidases and proposed that this isoenzyme is a conceivable lignification specific peroxidase. In this study, we cloned full-length cDNA of CWPO-C and investigated the transcription of CWPO-C gene in various organs and the localization of CWPO-C protein in the differentiating xylem of poplar stem.
-
lignin dehydrogenative polymerization mechanism a poplar cell wall peroxidase directly oxidizes polymer lignin and produces in vitro dehydrogenative polymer rich in β o 4 linkage
FEBS Letters, 2004Co-Authors: Shinya Sasaki, Tomoaki Nishida, Yuji Tsutsumi, Ryuichiro KondoAbstract:An investigation was performed to determine whether lignin dehydrogenative polymerization proceeds via radical mediation or direct oxidation by peroxidases. It was found that coniferyl Alcohol radical transferred quickly to Sinapyl Alcohol. The transfer to syringaresinol was slower, however, the transfer to polymeric lignols occurred very slightly. This result suggests that the radical mediator theory does not sufficiently explain the mechanism for dehydrogenative polymerization of lignin. A cationic cell wall peroxidase (CWPO-C) from poplar (Populus alba L.) callus showed a strong substrate preference for Sinapyl Alcohol and the Sinapyl Alcohol dimer, syringaresinol. Moreover, CWPO-C was capable of oxidizing high-molecular-weight Sinapyl Alcohol polymers and ferrocytochrome c. Therefore, the CWPO-C characteristics are important to produce polymer lignin. The results suggest that CWPO-C may be a peroxidase isoenzyme responsible for the lignification of plant cell walls.
John Ralph - One of the best experts on this subject based on the ideXlab platform.
-
Monolignol and monolignol hydroxycinnamate conjugate concentrations released from TX08001 and Della stems by DFRC.
2018Co-Authors: Brian A. Mckinley, John Ralph, Sara N. Olson, Kimberley B. Ritter, Dustin W. Herb, Steven D. Karlen, William L. Rooney, John E. MulletAbstract:Error bars represent standard error of mean. H; 4-hydroxycinnamyl Alcohol, G; coniferyl Alcohol, S; Sinapyl Alcohol, G-DHpCA; coniferyl dihydro-p-coumarate, G-DHFA; coniferyl dihydroferulate, S-DHpCA; Sinapyl dihydro-p-coumarate, S-DHFA; Sinapyl dihydroferulate, all as their diacetates. Data were obtained from two technical replicates of two biological replicates for both TX08001 and Della (experiments 2 and 3).
-
syringyl lignin production in conifers proof of concept in a pine tracheary element system
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Armin Wagner, Yuki Tobimatsu, Barbara Geddes, Lorelle Phillips, Heather Flint, Fachuang Lu, John Ralph, Fachuang Lu, John RalphAbstract:Conifers (softwoods) naturally lack syringyl units in their lignins, rendering lignocellulosic materials from such species more difficult to process than syringyl-rich hardwood species. Using a transformable Pinus radiata tracheary element (TE) system as an experimental platform, we investigated whether metabolic engineering can be used to create syringyl lignin in conifers. Pyrolysis-GC/MS and 2D-NMR analysis of P. radiata TE cultures transformed to express ferulate 5-hydroxylase (F5H) and caffeic acid O-methyltransferase (COMT) from Liquidambar styraciflua confirmed the production and incorporation of Sinapyl Alcohol into the lignin polymer. Transformation with F5H was sufficient for the production of syringyl lignin in TEs, but cotransformation with COMT improved its formation. In addition, lower levels of the pathway intermediate 5-hydroxyconiferyl Alcohol were evidenced in cotransformation experiments, indicating that the introduction of the COMT overcame the inefficiency of the native pine methyltransferases for supporting Sinapyl Alcohol production.Our results provide the proof of concept that it is possible to generate a lignin polymer that contains syringyl units in softwood species such as P. radiata, suggesting that it might be possible to retain the outstanding fiber properties of softwoods while imbuing them with the lignin characteristics of hardwoods that are more favorable for industrial processing.
-
Molecular and biochemical basis for stress-induced accumulation of free and bound p-coumaraldehyde in cucumber.
Plant physiology, 2011Co-Authors: Marina Varbanova, John Ralph, Katie Porter, Raymond Hammerschmidt, A. Daniel Jones, Brad DayAbstract:To elucidate the genetic and biochemical regulation of elicitor-induced p-coumaraldehyde accumulation in plants, we undertook a multifaceted approach to characterize the metabolic flux through the phenylpropanoid pathway via the characterization and chemical analysis of the metabolites in the p-coumaryl, coniferyl, and Sinapyl Alcohol branches of this pathway. Here, we report the identification and characterization of four cinnamyl Alcohol dehydrogenases (CADs) from cucumber (Cucumis sativus) with low activity toward p-coumaraldehyde yet exhibiting significant activity toward other phenylpropanoid hydroxycinnamaldehydes. As part of this analysis, we identified and characterized the activity of a hydroxycinnamoyl-coenzyme A:shikimate hydroxycinnamoyl transferase (HCT) capable of utilizing shikimate and p-coumaroyl-coenzyme A to generate p-coumaroyl shikimate. Following pectinase treatment of cucumber, we observed the rapid accumulation of p-coumaraldehyde, likely the result of low aldehyde reductase activity (i.e. Alcohol dehydrogenase in the reverse reaction) of CsCAD enzymes on p-coumaraldehyde. In parallel, we noted a concomitant reduction in the activity of CsHCT. Taken together, our findings support the hypothesis that the up-regulation of the phenylpropanoid pathway upon abiotic stress greatly enhances the overall p-coumaryl Alcohol branch of the pathway. The data presented here point to a role for CsHCT (as well as, presumably, p-coumarate 3-hydroxylase) as a control point in the regulation of the coniferyl and Sinapyl Alcohol branches of this pathway. This mechanism represents a potentially evolutionarily conserved process to efficiently and quickly respond to biotic and abiotic stresses in cucurbit plants, resulting in the rapid lignification of affected tissues.
-
Molecular and Biochemical Basis for Stress-Induced Accumulation of Free and Bound p-Coumaraldehyde
2011Co-Authors: Marina Varbanova, John Ralph, Katie Porter, Raymond Hammerschmidt, A. Daniel Jones, Brad DayAbstract:To elucidate the genetic and biochemical regulation of elicitor-induced p -coumaraldehyde accumulation in plants, we undertook a multifaceted approach to characterize the metabolic flux through the phenylpropanoid pathway via the characterization and chemical analysis of the metabolites in the p-coumaryl, coniferyl, and Sinapyl Alcohol branches of this pathway. Here, we report the identification and characterization of four cinnamyl Alcohol dehydrogenases (CADs) from cucumber (Cucumis sativus) with low activity toward p-coumaraldehyde yet exhibiting significant activity toward other phenylpropanoid hydroxycinnamaldehydes. As part of this analysis, we identified and characterized the activity of a hydroxycinnamoyl-coenzyme A:shikimate hydroxycinnamoyl transferase (HCT) capable of utilizing shikimate and p-coumaroyl-coenzyme A to generate p-coumaroyl shikimate. Following pectinase treatment of cucumber, we observed the rapid accumulation of p-coumaraldehyde, likely the result of low aldehyde reductase activity (i.e. Alcohol dehydrogenase in the reverse reaction) of CsCAD enzymes on p-coumaraldehyde. In parallel, we noted a concomitant reduction in the activity of CsHCT. Taken together, our findings support the hypothesis that the up-regulation of the phenylpropanoid pathway upon abiotic stress greatly enhances the overall p-coumaryl Alcohol branch of the pathway. The data presented here point to a role for CsHCT (as well as, presumably, p-coumarate 3-hydroxylase) as a control point in the regulation of the coniferyl and Sinapyl Alcohol branches of this pathway. This mechanism represents a potentially evolutionarily conserved process to efficiently and quickly respond to biotic and abiotic stresses in cucurbit plants, resulting in the rapid lignification of affected tissues.
-
Sequencing around 5-Hydroxyconiferyl Alcohol-Derived Units in Caffeic Acid O-Methyltransferase-Deficient Poplar Lignins
Plant Physiology, 2010Co-Authors: Jane M Marita, Catherine Lapierre, John Ralph, Kris Morreel, Wout Boerjan, Lise Jouanin, Kris Morreel, Wout Boerjan, John RalphAbstract:Caffeic acid O-methyltransferase (COMT) is a bifunctional enzyme that methylates the 5- and 3-hydroxyl positions on the aromatic ring of monolignol precursors, with a preference for 5-hydroxyconiferaldehyde, on the way to producing Sinapyl Alcohol. Lignins in COMT-deficient plants contain benzodioxane substructures due to the incorporation of 5-hydroxyconiferyl Alcohol (5-OH-CA), as a monomer, into the lignin polymer. The derivatization followed by reductive cleavage method can be used to detect and determine benzodioxane structures because of their total survival under this degradation method. Moreover, partial sequencing information for 5-OH-CA incorporation into lignin can be derived from detection or isolation and structural analysis of the resulting benzodioxane products. Results from a modified derivatization followed by reductive cleavage analysis of COMT-deficient lignins provide evidence that 5-OH-CA cross couples (at its beta-position) with syringyl and guaiacyl units (at their O-4-positions) in the growing lignin polymer and then either coniferyl or Sinapyl Alcohol, or another 5-hydroxyconiferyl monomer, adds to the resulting 5-hydroxyguaiacyl terminus, producing the benzodioxane. This new terminus may also become etherified by coupling with further monolignols, incorporating the 5-OH-CA integrally into the lignin structure.
Susumu Ohira - One of the best experts on this subject based on the ideXlab platform.
-
Total synthesis of cleomiscosin C via a regioselective cycloaddition reaction of o-quinone
Tetrahedron Letters, 2008Co-Authors: Atsuhito Kuboki, Tetsuya Arishige, Chie Maeda, Kohei Kuyama, Mami Hamabata, Susumu OhiraAbstract:We have achieved total synthesis of cleomiscosin C (aquillochin) through regioselective cycloaddition of o-quinone and protected Sinapyl Alcohol as a key step. During preparation of o-quinone from phenol by IBX oxidation, silyl substituents adjacent to the phenolic hydroxyl group afforded effective inhibition of an undesired oxidative elimination.
-
Reversal of the regioselectivity in a cycloaddition of o-quinones by varying the position of alkoxy substituents
Tetrahedron Letters, 2008Co-Authors: Atsuhito Kuboki, Toru Yamamoto, Mamie Taira, Tetsuya Arishige, Kohei Kuyama, Mami Hamabata, Rina Konishi, Mutsumi Shirahama, Takeya Hiramatsu, Susumu OhiraAbstract:We have investigated the regioselective cycloaddition of o-quinones 1b–e with the protected Sinapyl Alcohol 2. It was found that the position of the alkoxy substituent on the o-quinone ring controlled the regioselectivity of the cycloaddition. In addition, our reported procedure for determining the location of the side chains on 1,4-benzodioxanes has been improved.
-
Total synthesis of (±)-nitidanin and novel procedures for determination of the location of the side chains on 1,4-benzodioxane
Tetrahedron Letters, 2007Co-Authors: Atsuhito Kuboki, Toru Yamamoto, Mamie Taira, Tetsuya Arishige, Susumu OhiraAbstract:Regioselective cycloaddition of o-quinone 4 and protected Sinapyl Alcohol 2 gave 1,4-benzodioxane 5, which was converted to (±)-nitidanin (6), an antimalarial compound. Two novel procedures were developed to determine the location of the side chains of the adduct (5) based on partial ring cleavage.
Kris Morreel - One of the best experts on this subject based on the ideXlab platform.
-
syringyl lignin is unaltered by severe Sinapyl Alcohol dehydrogenase suppression in tobacco
The Plant Cell, 2011Co-Authors: Abdellah Barakate, Catherine Lapierre, Kris Morreel, Jennifer Stephens, Alison Goldie, W N Hunter, David Marshall, Robert D Hancock, Kris MorreelAbstract:The manipulation of lignin could, in principle, facilitate efficient biofuel production from plant biomass. Despite intensive study of the lignin pathway, uncertainty exists about the enzyme catalyzing the last step in syringyl (S) monolignol biosynthesis, the reduction of sinapaldehyde to Sinapyl Alcohol. Traditional schemes of the pathway suggested that both guaiacyl (G) and S monolignols are produced by a single substrate-versatile enzyme, cinnamyl Alcohol dehydrogenase (CAD). This was challenged by the discovery of a novel Sinapyl Alcohol dehydrogenase (SAD) that preferentially uses sinapaldehyde as a substrate and that was claimed to regulate S lignin biosynthesis in angiosperms. Consequently, most pathway schemes now show SAD (or SAD and CAD) at the sinapaldehyde reduction step, although functional evidence is lacking. We cloned SAD from tobacco (Nicotiana tabacum) and suppressed it in transgenic plants using RNA interference‐inducing vectors. Characterization of lignin in the woody stems shows no change to content, composition, or structure, and S lignin is normal. By contrast, plants additionally suppressed in CAD have changes to lignin structure and S:G ratio and have increased sinapaldehyde in lignin, similar to plants suppressed in CAD alone. These data demonstrate that CAD, not SAD, is the enzyme responsible for S lignin biosynthesis in woody angiosperm xylem.
-
Sequencing around 5-Hydroxyconiferyl Alcohol-Derived Units in Caffeic Acid O-Methyltransferase-Deficient Poplar Lignins
Plant Physiology, 2010Co-Authors: Jane M Marita, Catherine Lapierre, John Ralph, Kris Morreel, Wout Boerjan, Lise Jouanin, Kris Morreel, Wout Boerjan, John RalphAbstract:Caffeic acid O-methyltransferase (COMT) is a bifunctional enzyme that methylates the 5- and 3-hydroxyl positions on the aromatic ring of monolignol precursors, with a preference for 5-hydroxyconiferaldehyde, on the way to producing Sinapyl Alcohol. Lignins in COMT-deficient plants contain benzodioxane substructures due to the incorporation of 5-hydroxyconiferyl Alcohol (5-OH-CA), as a monomer, into the lignin polymer. The derivatization followed by reductive cleavage method can be used to detect and determine benzodioxane structures because of their total survival under this degradation method. Moreover, partial sequencing information for 5-OH-CA incorporation into lignin can be derived from detection or isolation and structural analysis of the resulting benzodioxane products. Results from a modified derivatization followed by reductive cleavage analysis of COMT-deficient lignins provide evidence that 5-OH-CA cross couples (at its beta-position) with syringyl and guaiacyl units (at their O-4-positions) in the growing lignin polymer and then either coniferyl or Sinapyl Alcohol, or another 5-hydroxyconiferyl monomer, adds to the resulting 5-hydroxyguaiacyl terminus, producing the benzodioxane. This new terminus may also become etherified by coupling with further monolignols, incorporating the 5-OH-CA integrally into the lignin structure.
-
Sequencing around 5-Hydroxyconiferyl Alcohol-Derived Units in Caffeic Acid O-Methyltransferase-Deficient
2010Co-Authors: Poplar Lignins, Catherine Lapierre, Lise Jouanin, Jane M Marita, Kris Morreel, Wout Boerjan, John RalphAbstract:Caffeic acid O-methyltransferase (COMT) is a bifunctional enzyme that methylates the 5- and 3-hydroxyl positions on the aromatic ring of monolignol precursors, with a preference for 5-hydroxyconiferaldehyde, on the way to producing Sinapyl Alcohol. Lignins in COMT-deficient plants contain benzodioxane substructures due to the incorporation of 5-hydroxyconiferyl Alcohol (5-OH-CA), as a monomer, into the lignin polymer. The derivatization followed by reductive cleavage method can be used to detect and determine benzodioxane structures because of their total survival under this degradation method. Moreover, partial sequencing information for 5-OH-CA incorporation into lignin can be derived from detection or isolation and structural analysis of the resulting benzodioxane products. Results from a modified derivatization followed by reductive cleavage analysis of COMT-deficient lignins provide evidence that 5-OH-CA cross couples (at its b-position) with syringyl and guaiacyl units (at their O-4-positions) in the growing lignin polymer and then either coniferyl or Sinapyl Alcohol, or another 5-hydroxyconiferyl monomer, adds to the resulting 5-hydroxyguaiacyl terminus, producing the benzodioxane. This new terminus may also become etherified by coupling with further monolignols, incorporating the 5-OH-CA integrally into the lignin structure.
-
preparation and relevance of a cross coupling product between Sinapyl Alcohol and Sinapyl p hydroxybenzoate
Organic and Biomolecular Chemistry, 2004Co-Authors: Fachuang Lu, John Ralph, Kris Morreel, Eric Messens, Wout BoerjanAbstract:Cross-coupling of Sinapyl p-hydroxybenzoate and Sinapyl Alcohol produces an 8-8-cross-coupled product that is also detected in lignifying poplar tissues, implicating Sinapyl p-hydroxybenzoate as a lignin precursor.
Ryuichiro Kondo - One of the best experts on this subject based on the ideXlab platform.
-
identification of tyr74 and tyr177 as substrate oxidation sites in cationic cell wall bound peroxidase from populus alba l
FEBS Journal, 2012Co-Authors: Jun Shigeto, Yuji Tsutsumi, Yoshitaka Itoh, Ryuichiro KondoAbstract:Cationic cell wall-bound peroxidase (CWPO-C) has the capability to oxidize Sinapyl Alcohol, ferrocytochrome c, and synthetic lignin polymers, unlike most peroxidases that have been characterized in flowering plants, such as horseradish peroxidase and Arabidopsis thaliana peroxidase A2. It has been suggested that the oxidation site is located on the CWPO-C surface, and homology modeling and chemically modified CWPO-C studies suggest that Tyr74 and/or Tyr177 are possible participants in the catalytic site. The present study clarifies the importance of these Tyr residues for substrate oxidation, using recombinant CWPO-C and recombinant mutant CWPO-C with phenylalanine substitution(s) for tyrosine. Such recombinant proteins, produced in Escherichia coli as inclusion bodies, were successfully refolded to yield the active form, and purified recombinant protein solutions exhibited typical spectra of high-spin ferric protein and displayed H2O2-dependent oxidation of guaiacol, 2,6-dimethoxyphenol, and syringaldazine. Measurement of peroxidase activity with these guaiacyl and syringyl compounds as reducing substrates indicated that a single mutation, Y74F or Y177F, resulted in substantial loss of oxidation activity (∼ 40–60% and 82%, respectively). Also, over 95% of the oxidation activity was lost with a double mutation, Y74F/Y177F. These results indicated that Tyr74 and Tyr177, rather than the heme pocket, play a central role in the oxidation of these substrates. This is the first report of active residues on an enzyme surface being identified in a plant peroxidase. This study also suggests that Sinapyl Alcohol incorporation into lignin is performed by a peroxidase that generates Tyr radicals on its surface.
-
the cationic cell wall peroxidase having oxidation ability for polymeric substrate participates in the late stage of lignification of populus alba l
Plant Molecular Biology, 2006Co-Authors: Shinya Sasaki, Keiichi Baba, Tomoaki Nishida, Yuji Tsutsumi, Ryuichiro KondoAbstract:Previously we reported that purified Cell Wall Peroxidase-Cationic (CWPO-C) from poplar callus (Populus alba L.) oxidizes Sinapyl Alcohol and polymeric substrate unlike other plant peroxidases and proposed that this isoenzyme is a conceivable lignification specific peroxidase. In this study, we cloned full-length cDNA of CWPO-C and investigated the transcription of CWPO-C gene in various organs and the localization of CWPO-C protein in the differentiating xylem of poplar stem.
-
lignin dehydrogenative polymerization mechanism a poplar cell wall peroxidase directly oxidizes polymer lignin and produces in vitro dehydrogenative polymer rich in β o 4 linkage
FEBS Letters, 2004Co-Authors: Shinya Sasaki, Tomoaki Nishida, Yuji Tsutsumi, Ryuichiro KondoAbstract:An investigation was performed to determine whether lignin dehydrogenative polymerization proceeds via radical mediation or direct oxidation by peroxidases. It was found that coniferyl Alcohol radical transferred quickly to Sinapyl Alcohol. The transfer to syringaresinol was slower, however, the transfer to polymeric lignols occurred very slightly. This result suggests that the radical mediator theory does not sufficiently explain the mechanism for dehydrogenative polymerization of lignin. A cationic cell wall peroxidase (CWPO-C) from poplar (Populus alba L.) callus showed a strong substrate preference for Sinapyl Alcohol and the Sinapyl Alcohol dimer, syringaresinol. Moreover, CWPO-C was capable of oxidizing high-molecular-weight Sinapyl Alcohol polymers and ferrocytochrome c. Therefore, the CWPO-C characteristics are important to produce polymer lignin. The results suggest that CWPO-C may be a peroxidase isoenzyme responsible for the lignification of plant cell walls.
-
the difference of reactivity between syringyl lignin and guaiacyl lignin in alkaline systems
Holzforschung, 1995Co-Authors: Yuji Tsutsumi, Kokki Sakai, Ryuichiro Kondo, Hiroyuki ImamuraAbstract:The difference of reactivity between syringyl lignin and guaiacyl lignin in alkaline systems were investigated by using syringyl and guaiacyl types of β-aryl ether lignin model compounds, softwood and hardwood dioxane lignins, and softwood and hardwood meals. In the lignin model study, β-aryl ether of syringyl lignin model was cleaved much faster than that of guaiacyl lignin model by soda and soda/anthraquinone treatment. The formation of coniferyl Alcohol and Sinapyl Alcohol from guaiacyl lignin model and syringyl lignin model, respectively, was almost proportional to the cleavage of β-aryl ether under these conditions. Based on the model studies, coniferyl Alcohol and Sinapyl Alcohol from isolated lignin and protolignin by soda and soda/anthraquinone treatments were determined in order to evaluate the extent of β-aryl ether cleavage in the terminal units of lignin. The results in both the dioxane lignins study and the wood meals study also indicate that β-aryl ether of syringyl lignin is cleaved much more easily than that of guaiacyl lignin and that there is no difference of reactivity of guaiacyl lignin in hardwood lignin and softwood lignin. This high reactivity of syringyl lignin may contribute the faster delignification rate of hardwood than softwood.
-
reaction of syringylglycerol β syringyl ether type of lignin model compounds in alkaline medium
Journal of Wood Chemistry and Technology, 1993Co-Authors: Yuji Tsutsumi, Ryuichiro Kondo, Hiroyuki ImamuraAbstract:Abstract Reactions of three kind of syringylglycerol- β-syringyl ether type model compounds under alkaline medium were investigated. Sinapyl Alcohol and β-hydroxypropiosyringone were formed as phenyl propanoid moieties from syringylglycerol- β-(methyl-syringyl) ether 1 by the β-aryl ether cleavage under soda treatment, while only Sinapyl Alcohol was formed from syringylglycerol- β-syringyl ether 2. The formation of both two degradation products are quite interesting because there is no nucleophilic additives in soda liquor. A possible reaction mechanisms for the β-aryl cleavage of syringylglycerol-β-syringyl ether type is homolytical cleavage via quinone methide.
