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Glycoside Hydrolase Family 62
| Glycoside Hydrolase Family GH62 | |
| Clan | GH-F |
| Mechanism | assumed to be inverting |
| Active site residues | inferred |
| CAZy DB link | |
| http://www.cazy.org/fam/GH62.html | |
Substrate specificities
This small family comprises an equal number of eukaryotic and prokaryotic enzymes. All the characterized enzymes in this family are arabinofuranosidases that specifically cleave either alpha1,2 or alpha1,3 L-arabinofuranose side chains from xylans [1, 2]. The enzyme will not act on xylose moieties in xylan that are decorated at both O2 and O3 with an arabinose side chain. The enzyme also displays no non-specific arabinofuranosidase activity; for example it does not hydrolyse 4-nitrophenyl-alpha-L-arabinofuranose. Several of these enzymes contain cellulose #1 or xylan #2 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 (ClanF), which is an inverting family. Similarly, although the catalytic residues have not been determined using either biochemical or mutagenesis strategies, the identity of these residues is 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 [3] predicts that the catalytic general acid and base will be a Glu and Asp, respectively, while a second Asp modulates the pKa of the general acid.
Catalytic Residues
Three-dimensional structures
Family Firsts
- First sterochemistry determination
- Cite some reference here, with a short explanation [1].
- First catalytic nucleophile identification
- First general acid/base residue identification
- First 3-D structure
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References
- Comfort DA, Bobrov KS, Ivanen DR, Shabalin KA, Harris JM, Kulminskaya AA, Brumer H, and Kelly RM. (2007). Biochemical analysis of Thermotoga maritima GH36 alpha-galactosidase (TmGalA) confirms the mechanistic commonality of clan GH-D glycoside hydrolases. Biochemistry. 2007;46(11):3319-30. DOI:10.1021/bi061521n |