Glycoside Hydrolase Family 9

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• Author: ^^^David Wilson^^^
• Responsible Curator: ^^^David Wilson^^^

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Glycoside Hydrolase Family GHnn
Clan	GH-x
Mechanism inverting
Active site residues	known/
CAZy DB link
http://www.cazy.org/fam/GHnn.html

Substrate specificities

Content is to be added here. GH Family 9 is an inverting glycohydrolase family that mainly contains cellulases and is the second largest cellulase family. It contains mainly endoglucanases with a few processive endoglucanases. All of the processive endoglucanases contain a family 3c CBM rigidly attached to the C-terminus of the family 9 catalytic domain (cd). This domain is part of the active site and is essential for processivity (1) CBM3c domains bind weakly to cellulose as they lack several of the conserved aromatic residues that are important for cellulose binding in family 3a and family 3b members (2). All known plant cellulases belong to family 9, and most of the other members are eubacterial although there are two archael members and some fungal, earthworm, arthropod, chordate, echinoderma and molusk members (http://www.cazy.org/fam/acc_GH.html). There are two subgroups in family 9, E1 which contains only cellulases from bacteria, including ones from both aerobes and anaeobes, and E2 which includes some bacterial and all nonbacterial cellulases (3). An evolutionary study shows that the eucaryote members contain two monophyletic groups that are amcient; one including all anamal members and the other including all plant members (4). All known processive endoglucanase genes are in subgroup E1.

This is an example of how to make references to a journal article [1]. (See the References section below). Multiple references can go in the same place like this [1, 2]. You can even cite books using just the ISBN [3]. References that are not in PubMed can be typed in by hand [4].

Kinetics and Mechanism

Content is to be added here. All known family 9 cd structures have an ( a / a ) 6 barrel fold that contains an open active site cleft that contains at least six sugar binding subsites -4 to +2 (1,5). There is a conserved Glu residue that functions as the catalytic acid and two conserved Asp residues that bind the catalytic water, with one functioning as the catalytic base and mutation of the other also greatly reduces activity on all substrates (6). The processive endoglucanase,Cel9A from Thermobifda fusca, has high activity on bacterial cellulose and is the only cellulase tested that can degrade crystalline regions in bacterial cellulose by itself although it prefers amorphous regions (7). A related cellulase in Clostridium phytofermentans, which is the only family 9 cellulase encoded in its genome, has been shown to be essential for cellulose degradation by this organism. This is the only case where a single cellulase has been shown to be essential for growth on cellulose (8).

Catalytic Residues

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Three-dimensional structures

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Family Firsts

First sterochemistry determination

Cite some reference here, with a short (1-2 sentence) explanation [1].

First catalytic nucleophile identification

Cite some reference here, with a short (1-2 sentence) explanation [4].

First general acid/base residue identification

Cite some reference here, with a short (1-2 sentence) explanation [2].

First 3-D structure

Cite some reference here, with a short (1-2 sentence) explanation [3].

References

1. 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 |
2. He S and Withers SG. (1997). Assignment of sweet almond beta-glucosidase as a family 1 glycosidase and identification of its active site nucleophile. J Biol Chem. 1997;272(40):24864-7. DOI:10.1074/jbc.272.40.24864 |

4. Sinnott, M.L. (1990) Catalytic mechanisms of enzymic glycosyl transfer. Chem. Rev. 90, 1171-1202. DOI: 10.1021/cr00105a006