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Difference between revisions of "Glycoside Hydrolase Family 45"
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== Substrate specificities == | == Substrate specificities == | ||
| − | [[Glycoside hydrolases]] of GH45 are endoglucanases (EC 3.2.1.4) | + | [[Glycoside hydrolases]] of GH45 are endoglucanases (EC 3.2.1.4); mainly the hydrolysis of soluble beta 1,4 glucans. |
| Line 42: | Line 42: | ||
== Three-dimensional structures == | == Three-dimensional structures == | ||
| − | + | The 3-D structure of canonical GH45 enzymes is a six-stranded b-barrel to which a seventh strand is appended. The structure differs from classical b-barrels in containing both paralle and anti-parallel b-strands. At the time of the first structure solution the fold had ony previously been observed in "Barwin"; a plant defense protein of unknown function. As is now expected for endo-enzymes, the active centre is located in an open substrate-binding groove. The original uncomplexes native structure had an | |
Revision as of 11:45, 4 October 2010
This page is currently under construction. This means that the Responsible Curator has deemed that the page's content is not quite up to CAZypedia's standards for full public consumption. All information should be considered to be under revision and may be subject to major changes.
- Author: ^^^Gideon Davies^^^
- Responsible Curator: ^^^Gideon Davies^^^
| Glycoside Hydrolase Family GH45 | |
| Clan | none |
| Mechanism | inverting |
| Active site residues | known (but see discussion) |
| CAZy DB link | |
| http://www.cazy.org/fam/GH45.html | |
Substrate specificities
Glycoside hydrolases of GH45 are endoglucanases (EC 3.2.1.4); mainly the hydrolysis of soluble beta 1,4 glucans.
Kinetics and Mechanism
The enzymes act with inversion of anomeric configuration to generate the alpha-D glucoside as product. Based upon the structure of the Humicola insolens endoglucanase V (now known as Cel45)[1][2] it was concluded that Asp121 acted as the general acid (implied by its hydrogen bonding to the glycosidic oxygen of a ligand in the +1 subsite) and that the most likely general base is Asp10, appropriately positioned "below" the sugar plane. As with many inverting enzymes the base assignment is less secure than that of the acid.
Catalytic Residues
"Classical" GH45 enzymes likely use twin carboxylates corresponding to Asp10 and 121 of the Humicola insolens endoglucanase V.
Three-dimensional structures
The 3-D structure of canonical GH45 enzymes is a six-stranded b-barrel to which a seventh strand is appended. The structure differs from classical b-barrels in containing both paralle and anti-parallel b-strands. At the time of the first structure solution the fold had ony previously been observed in "Barwin"; a plant defense protein of unknown function. As is now expected for endo-enzymes, the active centre is located in an open substrate-binding groove. The original uncomplexes native structure had an
Family Firsts
- First sterochemistry determination
- Cite some reference here, with a short (1-2 senetence) explanation [3].
- First general acid/base residue identification
- Cite some reference here, with a short (1-2 sentence) explanation [4].
- First 3-D structure
- The Humicola insolens EGV (now Cel45) by the Davies group [1].
References
- Davies GJ, Dodson GG, Hubbard RE, Tolley SP, Dauter Z, Wilson KS, Hjort C, Mikkelsen JM, Rasmussen G, and Schülein M. (1993). Structure and function of endoglucanase V. Nature. 1993;365(6444):362-4. DOI:10.1038/365362a0 |
- Davies GJ, Tolley SP, Henrissat B, Hjort C, and Schülein M. (1995). Structures of oligosaccharide-bound forms of the endoglucanase V from Humicola insolens at 1.9 A resolution. Biochemistry. 1995;34(49):16210-20. DOI:10.1021/bi00049a037 |
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Sinnott, M.L. (1990) Catalytic mechanisms of enzymic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006