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Difference between revisions of "Glycoside Hydrolase Family 43"
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== Substrate specificities == | == Substrate specificities == | ||
| − | + | The major activities reported for this family are alpha-L-arabinofuranosidases, endo-alpha-L-arabinanases (or endo-processive arabinanases) and beta-D-xylosidases. An enzyme with exo alpha1,3-galactanase has also been described. A significant number of enzymes in this family display both alpha-L-arabinofuranosidase and <math>b</math>-D-xylosidase activity using aryl-glycosides as substrates. It is likely that the natural activity of these enzymes is conferred by the aglycone component of the substrate. Indeed, the arabionofuranosidase activities already reported target very different glycans. Thus, the Bacillus subtilis enzyme arabinoxylan alpha-L-arabinofuranohydrolase specifically removes arabinofuranose side chains that are linked either alpha1,2 or alpha1,3 to backbone xylose residues <cite>#1</cite>, while the arabinoxylan arabinofuranohydrolase-D3 (AXHd3) from Bifidobacterium adolescentis will remove an alpha1,3-linked arabinofuranose from xylans where the xylose residue is substituted at both alpha1,2 and alpha1,3 with arabinose. By contrast some arabinofuranosidases are exo-alpha-L-arabinanases display. It should be noted that in several plant cell wall degrading organisms there has been a dramtic expansion in GH43 family enzymes, which may reflect a more extensive range of specificities than described to date. | |
== Kinetics and Mechanism == | == Kinetics and Mechanism == | ||
Revision as of 11:01, 22 July 2009
| Glycoside Hydrolase Family GH43 | |
| Clan | GH-F |
| Mechanism | inverting |
| Active site residues | not known |
| CAZy DB link | |
| http://www.cazy.org/fam/GH43.html | |
Substrate specificities
The major activities reported for this family are alpha-L-arabinofuranosidases, endo-alpha-L-arabinanases (or endo-processive arabinanases) and beta-D-xylosidases. An enzyme with exo alpha1,3-galactanase has also been described. A significant number of enzymes in this family display both alpha-L-arabinofuranosidase and <math>b</math>-D-xylosidase activity using aryl-glycosides as substrates. It is likely that the natural activity of these enzymes is conferred by the aglycone component of the substrate. Indeed, the arabionofuranosidase activities already reported target very different glycans. Thus, the Bacillus subtilis enzyme arabinoxylan alpha-L-arabinofuranohydrolase specifically removes arabinofuranose side chains that are linked either alpha1,2 or alpha1,3 to backbone xylose residues [1], while the arabinoxylan arabinofuranohydrolase-D3 (AXHd3) from Bifidobacterium adolescentis will remove an alpha1,3-linked arabinofuranose from xylans where the xylose residue is substituted at both alpha1,2 and alpha1,3 with arabinose. By contrast some arabinofuranosidases are exo-alpha-L-arabinanases display. It should be noted that in several plant cell wall degrading organisms there has been a dramtic expansion in GH43 family enzymes, which may reflect a more extensive range of specificities than described to date.
Kinetics and Mechanism
NMR, deploying arabinan as the substrate, showed that an endo-alpha1,5-arabinanase displays a single displacement or inverting mechanism
Catalytic Residues
Three-dimensional structures
Family Firsts
- First sterochemistry determination
- First catalytic nucleophile identification
- First general acid/base residue identification
- First 3-D structure
- alpha-L-Arabinanase from Cellvibrio japonicus [1].