Glycoside Hydrolase Family 164

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• Author: ^^^Zachary Armstrong^^^
• Responsible Curator: ^^^Gideon Davies^^^

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Glycoside Hydrolase Family GH164
Clan	GH-x
Mechanism	retaining/inverting
Active site residues	known/not known
CAZy DB link
http://www.cazy.org/GH164.html

Substrate specificities

The defining member of glycoside hydrolase family 164, a β-mannosidase from Bacteroidetes salyersiae (Bs164, GenbankID: EIY59668.1), was identified initially identified through rational bioinformatic selection of enzyme targets [1]. Although Bs164 was initially reported as an α-mannosidase, subsequent detailed biochemical characterization and structure determination revealed that was instead a β-mannosidase [2]. This enzyme is an exo-acting and is capable of cleaving mannooligos and β-mannosides[2].

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

To date only the structure of Bacteroidetes salyersiae β-mannosidase (Bs164) has been solved. Bs164 exists as a donut shaped trimer, see figure 1A. Each trimer-donut has an outer diameter of approximately 100 Å and an internal diameter of between 30 and 35 Å. The individual Bs164 chains contain three clearly defined domains: a modified (β/α)8 barrel, a domain containing a seven membered mixed β-sheet sandwiched between α-helices, and a β-sheet domain (Figure 1B). This domain architecture is quite similar to that seen for family GH42 enzymes [3], but is previously unseen for β-mannosidases.

Figure 1. The trimeric structure of Bs164 is shown in panel A. All three protomers are shown with a surface and each chain is displayed as a cartoon diagram coloured by domain. B shows the structure of one protomer. Domain A, which has a (β/α)8 fold, is shown in green with subdomain H is shown in magenta, domain B, containing a mixed β-sheet, is shown in red and the β-sandwich of domain C is shown in blue.

Family Firsts

First sterochemistry determination

Bacteroides salyersiae β-mannosidase by NMR [2]

First catalytic nucleophile identification

Bacteroides salyersiae β-mannosidase by 2-fluoromannose labeling and kinetic analysis of mutants [2]

First general acid/base residue identification

Bacteroides salyersiae β-mannosidase by kinetic analysis of mutants [2]

First 3-D structure of a GH1 enzyme

Bacteroides salyersiae β-mannosidase [2]

References

1. Helbert W, Poulet L, Drouillard S, Mathieu S, Loiodice M, Couturier M, Lombard V, Terrapon N, Turchetto J, Vincentelli R, and Henrissat B. (2019). Discovery of novel carbohydrate-active enzymes through the rational exploration of the protein sequences space. Proc Natl Acad Sci U S A. 2019;116(13):6063-6068. DOI:10.1073/pnas.1815791116 |
2. Armstrong Z and Davies GJ. (2020). Structure and function of Bs164 β-mannosidase from Bacteroides salyersiae the founding member of glycoside hydrolase family GH164. J Biol Chem. 2020;295(13):4316-4326. DOI:10.1074/jbc.RA119.011591 |
3. Hidaka M, Fushinobu S, Ohtsu N, Motoshima H, Matsuzawa H, Shoun H, and Wakagi T. (2002). Trimeric crystal structure of the glycoside hydrolase family 42 beta-galactosidase from Thermus thermophilus A4 and the structure of its complex with galactose. J Mol Biol. 2002;322(1):79-91. DOI:10.1016/s0022-2836(02)00746-5 |