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Glycoside Hydrolase Family 147
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| Glycoside Hydrolase Family GH147 | |
| Clan | GH-A |
| Mechanism | retaining |
| Active site residues | known |
| CAZy DB link | |
| https://www.cazy.org/GH147.html | |
Substrate specificities
The founding member of glycoside hydrolase family 147, BACOVA_05493 from Bacteroides ovatus is a β1,4-galactosidase. The enzyme demonstrates a preference towards longer oligosaccharides and β1,4-galactan, releasing galactopyranose from the oligosaccharide or polysaccharide chain. BACOVA_05493 is unable to hydrolyse β1,4-galactobiose [1].
Kinetics and Mechanism
1NMR analysis of the galactose product released from BACOVA_05493 action on galactotriose revealed cleavage with retention of anomeric stereochemistry [1]. The enzyme is believed to operate through a classical Koshland double-displacement mechanism.
Catalytic Residues
Hydrophobic cluster analysis showed that BACOVA_05493 is a member of Clan GH-A. Based on this assumption the catalytic nucleophile and general acid/base residues were proposed as Glu300 and Glu203, respectively. This hypothesis was supported by mutagenesis data showing that the E300A and E203A mutants were catalytically inactive [1].
Three-dimensional structures
Currently there is no crystal structure of any member of GH147, although sequence analysis and hydrophobic cluster analysis predicts a fold of an (α/β)8 barrel.
Family Firsts
- First stereochemistry determination
- BACOVA_05493 from B. ovatus was shown to have a retaining mechanism [1].
- First catalytic nucleophile identification
- BACOVA_05493 from B. ovatus [1].
- First general acid/base residue identification
- BACOVA_05493 from B. ovatus [1].
- First 3-D structure
- Currently no experimental structure is available, although BACOVA_05493 is predicted to fold into a (α/β)8 barrel [1].
References
- Luis AS, Briggs J, Zhang X, Farnell B, Ndeh D, Labourel A, Baslé A, Cartmell A, Terrapon N, Stott K, Lowe EC, McLean R, Shearer K, Schückel J, Venditto I, Ralet MC, Henrissat B, Martens EC, Mosimann SC, Abbott DW, and Gilbert HJ. (2018). Dietary pectic glycans are degraded by coordinated enzyme pathways in human colonic Bacteroides. Nat Microbiol. 2018;3(2):210-219. DOI:10.1038/s41564-017-0079-1 |