Glycoside Hydrolase Family 44

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• Author: ^^^Peter Reilly^^^
• Responsible Curator: ^^^Peter Reilly^^^

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Glycoside Hydrolase Family GH44
Clan	None specified, but Kitago et al. [1] and Nam et al. [2] suggest that it belongs to Clan GH-A.
Mechanism	Retaining
Active site residues	Catalytic proton donor/acceptor: Glu; catalytic nucleophile: Glu
CAZy DB link
https://www.cazy.org/GH44.html

Substrate specificities

Active on many substances, including cellooligosaccharides of DP4 and longer, carboxymethylcellulose, xylan, lichenan, Avicel (slightly), and xyloglucan, which appears to be the prime substrate [4,5].

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.

Catalytic Residues

Clostridium thermocellum endoglucanase: catalytic proton donor/acceptor: Glu186; catalytic nucleophile: Glu359 [1]. Protein from metagenomic library: catalytic proton donor/acceptor: Glu221; catalytic nucleophile: Glu393 [2].Clostridium acetobutylicum endoglucanase: catalytic proton donor/acceptor: Glu180; catalytic nucleophile: Glu352 [3].

Three-dimensional structures

The first three-dimensional structure was by Kitago et al. [1], who found a TIM-like barrel domain and a beta-sandwich domain in a Clostridium thermocellum endoglucanase. Similar structures were found by Nam et al. [2] in a protein from a metagenomic library and Warner et al. [3] in a Clostridium acetobutylicum endoglucanase. Ca and Zn ions are found as ligands [1].

Family Firsts

First stereochemistry determination

Kitago et al. [1] found that the enzyme acts by a retaining mechanism. They observed that beta-anomer was preferentially formed during cyclohexaitol hydrolysis.

First catalytic nucleophile identification

Kitago et al. [1], by testing activity of E359Q mutant.

First general acid/base residue identification

Kitago et al. [1], by testing activity of E186Q mutant.

First 3-D structure

Kitago et al. [1] of an endoglucanase from Clostridium thermocellum. It had a resolution of 0.96 Å and allowed the identification of the catalytic residues and the mechanism.

References

5. , Y., S. Karita, N. Watanabe, M. Kamiya, T. Aizawa, K. Sakka, and I. Tanaka. 2007. Crystal structure of Cel44A, a glycoside hydrolase family 44 endoglucanase from Clostridium thermocellum. J. Biol. Chem. 282, 35703–35711. doi: 10.1074/jbc.M706835200.

6. Nam, K. H., S.-J. Kim, and K. Y. Hwang. 2009. Crystal structure of CelM2, a bifunction­al glucanase–xylanase protein from a metagenomic library. Biochem. Biophys. Res. Comm. 383, 183–186. doi:10.1016/j.bbrc.2009.03.149.

7. Warner, C. D., J. A. Hoy, T. C. Shilling, M. J. Linnen, N. D. Ginder, C. F. Ford, R. B. Hon­zatko, and P. J. Reilly. 2010. Tertiary structure and characterization of a glycoside hydrolase family 44 endoglucanase from Clostridium acetobutylicum. Appl. Environ. Microbiol., 76, 338–346. doi:10.1128/AEM.02026-09.

8. Najmudin, S., C. I. Guerreiro, A. L. Carvalho, J. A. Prates, M. A. Correia, V. D. Alves, L. M. Ferreira, M. J. Romao, H. J. Gilbert, D. N. Bolam, and C. M. Fontes. 2006. J. Biol. Chem. 281, 8815–8828.