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Jay D Keasling - One of the best experts on this subject based on the ideXlab platform.
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xax1 from glycosyltransferase family 61 mediates xylosyltransfer to rice Xylan
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Dawn Chiniquy, Vaishali Sharma, Alex Schultink, Edward E K Baidoo, Carsten Rautengarten, Andrew Carroll, Peter Ulvskov, Jesper Harholt, Kun Cheng, Jay D KeaslingAbstract:Xylan is the second most abundant polysaccharide on Earth and represents an immense quantity of stored energy for biofuel production. Despite its importance, most of the enzymes that synthesize Xylan have yet to be identified. Xylans have a backbone of β-1,4–linked xylose residues with substitutions that include α-(1→2)–linked glucuronosyl, 4-O-methyl glucuronosyl, and α-1,2- and α-1,3-arabinofuranosyl residues. The substitutions are structurally diverse and vary by taxonomy, with grass Xylan representing a unique composition distinct from dicots and other monocots. To date, no enzyme has yet been identified that is specific to grass Xylan synthesis. We identified a xylose-deficient loss-of-function rice mutant in Os02g22380, a putative glycosyltransferase in a grass-specific subfamily of family GT61. We designate the mutant xax1 for xylosyl arabinosyl substitution of Xylan 1. Enzymatic fingerprinting of Xylan showed the specific absence in the mutant of a peak, which was isolated and determined by 1H-NMR to be (β-1,4-Xyl)4 with a β-Xylp-(1→2)-α-Araf-(1→3). Rice xax1 mutant plants are deficient in ferulic and coumaric acid, aromatic compounds known to be attached to arabinosyl residues in Xylan substituted with xylosyl residues. The xax1 mutant plants exhibit an increased extractability of Xylan and increased saccharification, probably reflecting a lower degree of diferulic cross-links. Activity assays with microsomes isolated from tobacco plants transiently expressing XAX1 demonstrated xylosyltransferase activity onto endogenous acceptors. Our results provide insight into grass Xylan synthesis and how substitutions may be modified for increased saccharification for biofuel generation.
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three members of the arabidopsis glycosyltransferase family 8 are Xylan glucuronosyltransferases
Plant Physiology, 2012Co-Authors: Emilie A Rennie, Edward E K Baidoo, Jay D Keasling, Sara Fasmer Hansen, Masood Z Hadi, Henrik Vibe SchellerAbstract:Xylan is a major component of the plant cell wall and the most abundant noncellulosic component in the secondary cell walls that constitute the largest part of plant biomass. Dicot glucuronoXylan consists of a linear backbone of β(1,4)-linked xylose residues substituted with α(1,2)-linked glucuronic acid (GlcA). Although several genes have been implicated in Xylan synthesis through mutant analyses, the biochemical mechanisms responsible for synthesizing Xylan are largely unknown. Here, we show evidence for biochemical activity of GUX1 (for GlcA substitution of Xylan 1), a member of Glycosyltransferase Family 8 in Arabidopsis (Arabidopsis thaliana) that is responsible for adding the glucuronosyl substitutions onto the Xylan backbone. GUX1 has characteristics typical of Golgi-localized glycosyltransferases and a Km for UDP-GlcA of 165 μm. GUX1 strongly favors xylohexaose as an acceptor over shorter xylooligosaccharides, and with xylohexaose as an acceptor, GlcA is almost exclusively added to the fifth xylose residue from the nonreducing end. We also show that several related proteins, GUX2 to GUX5 and Plant Glycogenin-like Starch Initiation Protein6, are Golgi localized and that only two of these proteins, GUX2 and GUX4, have activity as Xylan α-glucuronosyltransferases.
Edward E K Baidoo - One of the best experts on this subject based on the ideXlab platform.
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xax1 from glycosyltransferase family 61 mediates xylosyltransfer to rice Xylan
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Dawn Chiniquy, Vaishali Sharma, Alex Schultink, Edward E K Baidoo, Carsten Rautengarten, Andrew Carroll, Peter Ulvskov, Jesper Harholt, Kun Cheng, Jay D KeaslingAbstract:Xylan is the second most abundant polysaccharide on Earth and represents an immense quantity of stored energy for biofuel production. Despite its importance, most of the enzymes that synthesize Xylan have yet to be identified. Xylans have a backbone of β-1,4–linked xylose residues with substitutions that include α-(1→2)–linked glucuronosyl, 4-O-methyl glucuronosyl, and α-1,2- and α-1,3-arabinofuranosyl residues. The substitutions are structurally diverse and vary by taxonomy, with grass Xylan representing a unique composition distinct from dicots and other monocots. To date, no enzyme has yet been identified that is specific to grass Xylan synthesis. We identified a xylose-deficient loss-of-function rice mutant in Os02g22380, a putative glycosyltransferase in a grass-specific subfamily of family GT61. We designate the mutant xax1 for xylosyl arabinosyl substitution of Xylan 1. Enzymatic fingerprinting of Xylan showed the specific absence in the mutant of a peak, which was isolated and determined by 1H-NMR to be (β-1,4-Xyl)4 with a β-Xylp-(1→2)-α-Araf-(1→3). Rice xax1 mutant plants are deficient in ferulic and coumaric acid, aromatic compounds known to be attached to arabinosyl residues in Xylan substituted with xylosyl residues. The xax1 mutant plants exhibit an increased extractability of Xylan and increased saccharification, probably reflecting a lower degree of diferulic cross-links. Activity assays with microsomes isolated from tobacco plants transiently expressing XAX1 demonstrated xylosyltransferase activity onto endogenous acceptors. Our results provide insight into grass Xylan synthesis and how substitutions may be modified for increased saccharification for biofuel generation.
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three members of the arabidopsis glycosyltransferase family 8 are Xylan glucuronosyltransferases
Plant Physiology, 2012Co-Authors: Emilie A Rennie, Edward E K Baidoo, Jay D Keasling, Sara Fasmer Hansen, Masood Z Hadi, Henrik Vibe SchellerAbstract:Xylan is a major component of the plant cell wall and the most abundant noncellulosic component in the secondary cell walls that constitute the largest part of plant biomass. Dicot glucuronoXylan consists of a linear backbone of β(1,4)-linked xylose residues substituted with α(1,2)-linked glucuronic acid (GlcA). Although several genes have been implicated in Xylan synthesis through mutant analyses, the biochemical mechanisms responsible for synthesizing Xylan are largely unknown. Here, we show evidence for biochemical activity of GUX1 (for GlcA substitution of Xylan 1), a member of Glycosyltransferase Family 8 in Arabidopsis (Arabidopsis thaliana) that is responsible for adding the glucuronosyl substitutions onto the Xylan backbone. GUX1 has characteristics typical of Golgi-localized glycosyltransferases and a Km for UDP-GlcA of 165 μm. GUX1 strongly favors xylohexaose as an acceptor over shorter xylooligosaccharides, and with xylohexaose as an acceptor, GlcA is almost exclusively added to the fifth xylose residue from the nonreducing end. We also show that several related proteins, GUX2 to GUX5 and Plant Glycogenin-like Starch Initiation Protein6, are Golgi localized and that only two of these proteins, GUX2 and GUX4, have activity as Xylan α-glucuronosyltransferases.
Henrik Vibe Scheller - One of the best experts on this subject based on the ideXlab platform.
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three members of the arabidopsis glycosyltransferase family 8 are Xylan glucuronosyltransferases
Plant Physiology, 2012Co-Authors: Emilie A Rennie, Edward E K Baidoo, Jay D Keasling, Sara Fasmer Hansen, Masood Z Hadi, Henrik Vibe SchellerAbstract:Xylan is a major component of the plant cell wall and the most abundant noncellulosic component in the secondary cell walls that constitute the largest part of plant biomass. Dicot glucuronoXylan consists of a linear backbone of β(1,4)-linked xylose residues substituted with α(1,2)-linked glucuronic acid (GlcA). Although several genes have been implicated in Xylan synthesis through mutant analyses, the biochemical mechanisms responsible for synthesizing Xylan are largely unknown. Here, we show evidence for biochemical activity of GUX1 (for GlcA substitution of Xylan 1), a member of Glycosyltransferase Family 8 in Arabidopsis (Arabidopsis thaliana) that is responsible for adding the glucuronosyl substitutions onto the Xylan backbone. GUX1 has characteristics typical of Golgi-localized glycosyltransferases and a Km for UDP-GlcA of 165 μm. GUX1 strongly favors xylohexaose as an acceptor over shorter xylooligosaccharides, and with xylohexaose as an acceptor, GlcA is almost exclusively added to the fifth xylose residue from the nonreducing end. We also show that several related proteins, GUX2 to GUX5 and Plant Glycogenin-like Starch Initiation Protein6, are Golgi localized and that only two of these proteins, GUX2 and GUX4, have activity as Xylan α-glucuronosyltransferases.
Dawn Chiniquy - One of the best experts on this subject based on the ideXlab platform.
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xax1 from glycosyltransferase family 61 mediates xylosyltransfer to rice Xylan
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Dawn Chiniquy, Vaishali Sharma, Alex Schultink, Edward E K Baidoo, Carsten Rautengarten, Andrew Carroll, Peter Ulvskov, Jesper Harholt, Kun Cheng, Jay D KeaslingAbstract:Xylan is the second most abundant polysaccharide on Earth and represents an immense quantity of stored energy for biofuel production. Despite its importance, most of the enzymes that synthesize Xylan have yet to be identified. Xylans have a backbone of β-1,4–linked xylose residues with substitutions that include α-(1→2)–linked glucuronosyl, 4-O-methyl glucuronosyl, and α-1,2- and α-1,3-arabinofuranosyl residues. The substitutions are structurally diverse and vary by taxonomy, with grass Xylan representing a unique composition distinct from dicots and other monocots. To date, no enzyme has yet been identified that is specific to grass Xylan synthesis. We identified a xylose-deficient loss-of-function rice mutant in Os02g22380, a putative glycosyltransferase in a grass-specific subfamily of family GT61. We designate the mutant xax1 for xylosyl arabinosyl substitution of Xylan 1. Enzymatic fingerprinting of Xylan showed the specific absence in the mutant of a peak, which was isolated and determined by 1H-NMR to be (β-1,4-Xyl)4 with a β-Xylp-(1→2)-α-Araf-(1→3). Rice xax1 mutant plants are deficient in ferulic and coumaric acid, aromatic compounds known to be attached to arabinosyl residues in Xylan substituted with xylosyl residues. The xax1 mutant plants exhibit an increased extractability of Xylan and increased saccharification, probably reflecting a lower degree of diferulic cross-links. Activity assays with microsomes isolated from tobacco plants transiently expressing XAX1 demonstrated xylosyltransferase activity onto endogenous acceptors. Our results provide insight into grass Xylan synthesis and how substitutions may be modified for increased saccharification for biofuel generation.
Emilie A Rennie - One of the best experts on this subject based on the ideXlab platform.
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three members of the arabidopsis glycosyltransferase family 8 are Xylan glucuronosyltransferases
Plant Physiology, 2012Co-Authors: Emilie A Rennie, Edward E K Baidoo, Jay D Keasling, Sara Fasmer Hansen, Masood Z Hadi, Henrik Vibe SchellerAbstract:Xylan is a major component of the plant cell wall and the most abundant noncellulosic component in the secondary cell walls that constitute the largest part of plant biomass. Dicot glucuronoXylan consists of a linear backbone of β(1,4)-linked xylose residues substituted with α(1,2)-linked glucuronic acid (GlcA). Although several genes have been implicated in Xylan synthesis through mutant analyses, the biochemical mechanisms responsible for synthesizing Xylan are largely unknown. Here, we show evidence for biochemical activity of GUX1 (for GlcA substitution of Xylan 1), a member of Glycosyltransferase Family 8 in Arabidopsis (Arabidopsis thaliana) that is responsible for adding the glucuronosyl substitutions onto the Xylan backbone. GUX1 has characteristics typical of Golgi-localized glycosyltransferases and a Km for UDP-GlcA of 165 μm. GUX1 strongly favors xylohexaose as an acceptor over shorter xylooligosaccharides, and with xylohexaose as an acceptor, GlcA is almost exclusively added to the fifth xylose residue from the nonreducing end. We also show that several related proteins, GUX2 to GUX5 and Plant Glycogenin-like Starch Initiation Protein6, are Golgi localized and that only two of these proteins, GUX2 and GUX4, have activity as Xylan α-glucuronosyltransferases.
