2.4.1.B52: mixed-linkage glucan endotransglucosylase
This is an abbreviated version!
For detailed information about mixed-linkage glucan endotransglucosylase, go to the full flat file.
Reaction
transfers a (1->3),(1->4) mixed-linkage glucan to a xyloglucan =
Synonyms
BdTHX8, cellulose:xyloglucan endotransglucosylase, CXE, FvXTH9, grass-specific glycoside hydrolase family 16 endotransglucosylase/hydrolase, HTG, mixed-linkage glucan:xyloglucan endotransglucosylase, MLG:glucan endotransglucosylase, MLG:xyloglucan endotransglucosylase, More, MXE, XTH9
ECTree
2.4.1.B52 mixed-linkage glucan endotransglucosylaseAdvanced search results
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General Information on EC 2.4.1.B52 - mixed-linkage glucan endotransglucosylase
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GENERAL INFORMATION 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
evolution
malfunction
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Brachypodium distachyon shoots regenerated from transformed calli overexpressing BdTHX1 show an abnormal arrangement of vascular tissue and seedling-lethal phenotypes. These results indicate that the transcription factor BdTHX1 likely plays an important role in MLG biosynthesis and restructuring by regulating the expression of BdCSLF6 and BdXTH8
metabolism
physiological function
additional information
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BdXTH8 has a BdTHX1 transcription factor binding site in the 3' proximal region. BdXTH8 binding analysis with transcription factors, overview
evolution
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BdXTH8 is a member of this grass-specific clade of GH16 genes in Brachypodium distachyon. Gene BdXTH8 encodes a grass-specific glycoside hydrolase family 16 endotransglucosylase/hydrolase. BdXTH8 is a poalean XTH that preferentially exhibits MXE (EC 2.4.1.B52), a hetero-transglycosylase activity
evolution
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mixed-linkage glucan:xyloglucan endotransglucosylase (MXE) is one of the three activities of the recently characterised hetero-trans-beta-glucanase (HTG), which among land plants is known only from Equisetum species. The enzyme MXE belongs to the GH16 family
evolution
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XTHs are classified together with the lichenases, which hydrolyse mixed-linkage (1->3,1->4)-beta-D-glucans (MLG), in glycoside hydrolase family 16
metabolism
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a trihelix family transcription factor is associated with key genes in mixed-linkage glucan accumulation. Brachypodium distachyon trihelix family transcription factor (BdTHX1) is highly coexpressed with the Brachypodium distachyon CSLF6 gene (BdCSLF6), which suggests that BdTHX1 is involved in the regulation of mixed-linkage glucan (MLG) biosynthesis. The gene encoding a grass-specific glycoside hydrolase family 16 endotransglucosylase/hydrolase (BdXTH8) is bound by BdTHX1. BdTHX1 directly binds to an intronic region of BdCSLF6 and also to the 3' proximal region of BdXTH8. BdTHX1 likely plays an important role in MLG biosynthesis and restructuring by regulating the expression of BdCSLF6 and BdXTH8. BdTHX1 may regulate genes related to cell wall assembly or restructuring such as BdXTH8, and misregulation of BdTHX1 is detrimental to Brachypodium distachyon development
metabolism
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enzymes FvXTH9 and FvXTH6 display xyloglucan endotransglucosylase (XET, EC 2.4.1.207) activity towards various acceptor substrates using xyloglucan as the donor substrate. FvXTH9 also shows activity of mixed-linkage glucan:xyloglucan endotransglucosylase (MXE) and cellulose:xyloglucan endotransglucosylase (CXE). XTHs (xyloglucan endotransglucosylases/hydrolases) can catalyse the endolytic cleavage of xyloglucan polymers and the rejoining of the newly generated reducing ends to other xyloglucan molecules, which is referred to as xyloglucan endotransglucosylase (XET) activity. In addition, XTHs can also show xyloglucan endohydrolase (XEH) activity, where water is used as an acceptor, and thus the xyloglucan molecule is hydrolysed
physiological function
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among land-plant hemicelluloses, xyloglucan is ubiquitous, whereas mixed-linkage (1->3), (1->4)-beta-D-glucan, i.e. MLG, is confined to the Poales and Equisetales. The enzyme MLG:xyloglucan endotransglucosylase, MXE, grafts MLGto xyloglucan. MLG is absent in the most immature cells tested (callus culture) and highly prevalent in older tissues, whereas xyloglucan content is higher in young tissues
physiological function
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among land-plant hemicelluloses, xyloglucan is ubiquitous, whereas mixed-linkage (1->3), (1->4)-beta-D-glucan, i.e. MLG, is confined to the Poales and Equisetales. The enzyme MLG:xyloglucan endotransglucosylase, MXE, grafts MLGto xyloglucan. MLG is absent in the most immature cells tested (callus culture) and highly prevalent in older tissues, whereas xyloglucan content is higher in young tissues
physiological function
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BdXTH8 exhibits predominantly MLG:xyloglucan endotransglucosylase activity, a hetero-transglycosylation reaction, and can thus produce MLG-xyloglucan covalent bonds. It also has a lower xyloglucan:xyloglucan endotransglucosylase activity. Mixed-linkage glucan (MLG) is a polysaccharide that is highly abundant in grass endosperm cell walls and present at lower amounts in other tissues. BdXTH8 does not exhibit appreciable cellulose:xyloglucan endotransglucosylase (CXE) activity, with either insoluble (paper) cellulose or water-soluble cellulose acetate as donor substrate. The enzyme's main role in vivo is likely to be the making and/or breaking of MLG-xyloglucan covalent bonds that stably link two hemicelluloses of the grass cell wall and thus contribute to grass cell wall assembly and/or loosening
physiological function
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FvXTH9 and also FvXTH6 might promote strawberry fruit ripening by the modification of cell wall components. The level of anthocyanins such as pelargonidin-3-O-glucoside and pelargonidin-3-O-(6'-malonyl)-glucoside is significantly higher in the infiltrated fruits, similar to citric acid and ascorbic acid
