Glycoside Hydrolase Family 192

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• Author: Masahiro Nakajima
• Responsible Curator: Masahiro Nakajima

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Glycoside Hydrolase Family GH192
Clan	GH-S
Mechanism	inverting
Active site residues	not known
CAZy DB link
https://www.cazy.org/GH192.html

Substrate specificities

PgSGL1(H744_1c0224, KEGG) and PgSGL2(H744_2c1936, KEGG) from Photobacterium gaetbulicola and EeSGL1(A0A081KBI6, Uniprot) from Endozoicomonas elysicola are characterized. The three enzymes are specific to β-1,2-glucan among polysaccharides. They hydrolyze β-1,2-glucan endolytically to produce β-1,2-glucooligosaccharides [1].

Authors may get an idea of what to put in each field from Curator Approved Glycoside Hydrolase Families. (TIP: Right click with your mouse and open this link in a new browser window...)

Kinetics and Mechanism

PgSGL1 follows anomer-inverting mechanism, which is determined by measuring change of optical rotation during hydrolysis of β-1,2-glucan [1].

Catalytic Residues

E221(EeSGL1) is the putative general acid as this residue is structurally well-superimposed with the general acid (E262) in GH162 β-1,2-glucanase from Talaromyces funiculosus [2]. E221Q mutant shows drastic decrease in catalytic activity compared to the wild-type enzyme [1]. E221 is also conserved across other GH-S clan families including GH144, GH193, and GH194.
Similarly, D149 (EeSGL1) is a spatially conserved residue shared with several β-1,2-glucanases; GH144 (from Chitinophaga pinensis and Xanthomonas campestris pv. campestris) GH193 (from Sanguibacter keddieii), and GH194 (from P. gaetbulicala) [1, 3]. D149N mutant also shows drastically decreased activity against the wild-type enzyme. Although the D149N mutation significantly diminished enzymatic activity, a clear proton relay pathway directed toward the anomeric carbon at the cleavage site could not be definitively traced based on the current structural data.

Three-dimensional structures

A ligand-free structure of EeSGL1 is solved in 2025 [1].

Family Firsts

First stereochemistry determination

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First catalytic nucleophile identification

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First general acid/base residue identification

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First 3-D structure

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References

1. Nakajima M, Tanaka N, Motouchi S, Kobayashi K, Shimizu H, Abe K, Hosoyamada N, Abara N, Morimoto N, Hiramoto N, Nakata R, Takashima A, Hosoki M, Suzuki S, Shikano K, Fujimaru T, Imagawa S, Kawadai Y, Wang Z, Kitano Y, Nihira T, Nakai H, and Taguchi H. (2025). New glycoside hydrolase families of β-1,2-glucanases. Protein Sci. 2025;34(6):e70147. DOI:10.1002/pro.70147 |
2. Tanaka N, Nakajima M, Narukawa-Nara M, Matsunaga H, Kamisuki S, Aramasa H, Takahashi Y, Sugimoto N, Abe K, Terada T, Miyanaga A, Yamashita T, Sugawara F, Kamakura T, Komba S, Nakai H, and Taguchi H. (2019). Identification, characterization, and structural analyses of a fungal endo-β-1,2-glucanase reveal a new glycoside hydrolase family. J Biol Chem. 2019;294(19):7942-7965. DOI:10.1074/jbc.RA118.007087 |
3. Abe K, Nakajima M, Yamashita T, Matsunaga H, Kamisuki S, Nihira T, Takahashi Y, Sugimoto N, Miyanaga A, Nakai H, Arakawa T, Fushinobu S, and Taguchi H. (2017). Biochemical and structural analyses of a bacterial endo-β-1,2-glucanase reveal a new glycoside hydrolase family. J Biol Chem. 2017;292(18):7487-7506. DOI:10.1074/jbc.M116.762724 |