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Glycoside Hydrolase Family 45

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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

Content is to be added here.


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

  1. Davies GJ, Dodson GG, Hubbard RE, Tolley SP, Dauter Z, Wilson KS, Hjort C, Mikkelsen JM, Rasmussen G, and Schülein M. Structure and function of endoglucanase V. Nature. 1993 Sep 23;365(6444):362-4. DOI:10.1038/365362a0 | PubMed ID:8377830 | HubMed [Davies1993]
  2. Davies GJ, Tolley SP, Henrissat B, Hjort C, and Schülein M. Structures of oligosaccharide-bound forms of the endoglucanase V from Humicola insolens at 1.9 A resolution. Biochemistry. 1995 Dec 12;34(49):16210-20. PubMed ID:8519779 | HubMed [Davies1995]
  3. ISBN:978-0-240-52118-3 [3]
  4. Sinnott, M.L. (1990) Catalytic mechanisms of enzymic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006 [4]
All Medline abstracts: PubMed | HubMed
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