Glycoside Hydrolase Family 193

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• Author: Masahiro Nakajima
• Responsible Curator: Masahiro Nakajima

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Glycoside Hydrolase Family GH193
Clan	GH-S
Mechanism	inverting
Active site residues	not known
CAZy DB link
https://www.cazy.org/GH193.html

Substrate specificities

SkSGL(Sked_30460, KEGG) from Sanguibacter kedieii was characterized as reported in 2025 [1]. The enzyme specifically hydrolyzes β-1,2-glucan to produce β-1,2-glucooligosaccharides in an endolytic manner.

Kinetics and Mechanism

Hydrolysis of β-1,2-glucan by SkSGL suggests that the enzyme follows anomer-inverting mechanism [1]. Analysis of the change of the degree of optical rotation during hydrolysis of β-1,2-glucan and after addition of aqueous ammonia. Sharp decrease of the degree of optical rotation by aqueous ammonia is the same pattern as in the case of GH162 β-1,2-glucanase from Talaromyces funiculosus (TfSGL), an anomer-inverting enzyme.

Catalytic Residues

E246(SkSGL) 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].
D160(SkSGL) is one of the candidate for the general base as this residue is a spatially conserved residue shared with several β-1,2-glucanases; GH144 (from Chitinophaga pinensis and Xanthomonas campestris pv. campestris) GH192 (from P. gaetbulicola and Endozoicomonas elysicola), and GH194 (from P. gaetbulicala) [1, 3]. However, no complex structure with a substrate is available.

Three-dimensional structures

Currently not determined.

Family Firsts

First stereochemistry determination

A bacterial β-1,2-glucanase from S. kedieii by monitoring the change in optical rotation [1].

First catalytic nucleophile identification

not known.

First general acid/base residue identification

not known.

First 3-D structure

not determined.

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 |