Glycoside Hydrolase Family 189

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• Authors: Tomoko Masaike, Masahiro Nakajima, and Nobukiyo Tanaka
• Responsible Curator: Masahiro Nakajima

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Glycoside Hydrolase Family GH189
Clan	GH-x
Mechanism	retaining
Active site residues	known
CAZy DB link
https://www.cazy.org/GH189.html

Substrate specificities

The cyclization domain alone of cyclic β-1,2-glucan synthase from Thermoanaerobacter italicus (TiCGSCy) was identified, characterized and structurally analyzed as reported in 2024 [1]. This enzyme established the novel glycoside hydrolase family (GH) 189. This enzyme specifically catalyzes transglycosylation reactions on linear β-1,2-glucans (LβGs) and β-1,2-glucooligosaccharides (Sopns, where 'n' represents the degree of polymerization (DP)) with DP 6 or more [1]. In the deglycosylation step, intermolecular transglycosylation results in release of disproportionated linear products, while intramolecular transglycosylation results in cyclization of the substrates to release cyclic β-1,2-glucans (CβGs) [1].

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

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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. Cantarel BL, Coutinho PM, Rancurel C, Bernard T, Lombard V, and Henrissat B. (2009). The Carbohydrate-Active EnZymes database (CAZy): an expert resource for Glycogenomics. Nucleic Acids Res. 2009;37(Database issue):D233-8. DOI:10.1093/nar/gkn663 |

2. Davies, G.J. and Sinnott, M.L. (2008) Sorting the diverse: the sequence-based classifications of carbohydrate-active enzymes. The Biochemist, vol. 30, no. 4., pp. 26-32. DOI:10.1042/BIO03004026.