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Glycoside Hydrolase Family 62
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| Glycoside Hydrolase Family GH62 | |
| Clan | GH-F |
| Mechanism | assumed to be inverting |
| Active site residues | inferred |
| CAZy DB link | |
| https://www.cazy.org/GH62.html | |
Substrate specificities
This small family of glycoside hydrolases comprises an equal number of eukaryotic and prokaryotic enzymes. All the characterized enzymes in this family are arabinofuranosidases that specifically cleave either α-1,2 or α-1,3-L-arabinofuranose side chains from xylans [1, 2]. The enzymes will not act on xylose moieties in xylan that are decorated at both O2 and O3 with an arabinose side chain. The GH62 enzyme from Cellvibrio japonius also displays no non-specific arabinofuranosidase activity; for example it does not hydrolyse 4-nitrophenyl α-L-arabinofuranoside. Several of these enzymes contain cellulose-[1] or xylan-[3] binding CBMs.
Kinetics and Mechanism
While the catalytic mechanism of this family have not been formerly determined, likely reflecting the extremely quick rate of mutarotation displayed by arabinose, the enzyme is predicted to display a single displacement or inverting mechanism. This prediction is based on the location of GH62 in clan F, the same clan occupied by GH43, which is an inverting family. Prior to 3D structural data the catalytic residues were predicted from sequence homology with GH43 enzymes, given that both the catalytic mechanism and the catalytic apparatus are conserved in glycoside hydrolase families belonging to the same clan. Thus [4] predicts that the catalytic general acid and general base will be a Glu and Asp, respectively, while a second Asp modulates the pKa of the general acid.
Catalytic Residues
Predicted to be an Asp (general acid) and Glu (general base)
Three-dimensional structures
Based on its location in clan F, enzymes from family GH62s are predicted to display a 5-fold β-propeller fold
Family Firsts
- First sterochemistry determination
- No experimental proof.
- First general acid residue identification
- No experimental proof.
- First general base residue identification
- No experimental proof.
- First 3-D structure
- No experimental proof.
References
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